Since you seem to like Scripture so much:
I. We are One Family in Christ in Heaven and on Earth
Eph. 3:14-15- we are all one family ("Catholic") in heaven and on earth, united together, as children of the Father, through Jesus Christ. Our brothers and sisters who have gone to heaven before us are not a different family. We are one and the same family. This is why, in the Apostles Creed, we profess a belief in the "communion of saints." There cannot be a "communion" if there is no union. Loving beings, whether on earth or in heaven, are concerned for other beings, and this concern is reflected spiritually through prayers for one another.
Eph. 1:22-23; 5:23-32; Col. 1:18,24 - this family is in Jesus Christ, the head of the body, which is the Church.
1 Cor. 12:12,27; Rom. 12:5; Col. 3:15; Eph. 4:4 - we are the members of the one body of Christ, supernaturally linked together by our partaking of the Eucharist.
Rom. 8:35-39 - therefore, death does not separate the family of God and the love of Christ. We are still united with each other, even beyond death.
Matt. 17:3; Mark 9:4; Luke 9:30 - Jesus converses with "deceased" Moses and Elijah. They are more alive than the saints on earth.
Matt. 22:32; Mark 12:27; Luke 20:38 - God is the God of the living not the dead. The living on earth and in heaven are one family.
Luke 15:7,10 – if the angels and saints experience joy in heaven over our repentance, then they are still connected to us and are aware of our behavior.
John 15:1-6 - Jesus is the vine and we are the branches. The good branches are not cut off at death. They are alive in heaven.
1 Cor. 4:9 – because we can become a spectacle not only to men, but to angels as well, this indicates that angels are aware of our earthly activity. Those in heaven are connected to those on earth.
1 Cor. 12:26 - when one member suffers, all suffer. When one is honored, all rejoice. We are in this together as one family.
1 Cor 13:12; 1 John 3:2 - now we see in a mirror dimly, but in heaven we see face to face. The saints are more alive than we are!
Heb. 12:1 - we are surrounded by a great glory cloud (shekinah) of witnesses, our family in heaven. We are not separated. The “cloud of witnesses” (nephos marturon) refers to a great amphitheatre with the arena for the runners (us on earth), and many tiers of seats occupied by the saints (in heaven) rising up like a cloud. The “martures” are not mere spectators (“theatai”), but testifiers (witnesses) who testify from their own experience to God’s promises and cheer us on in our race to heaven. They are no less than our family in heaven.
1 Peter 2:9; Rev. 20:6 - we are a royal family of priests by virtue of baptism. We as priests intercede on behalf of each other.
2 Peter 1:4 - since God is the eternal family and we are His children, we are partakers of His divine nature as a united family.
1 Cor. 1:2; Rom. 1:7 - we are called to be saints. Saints refer to both those on earth and in heaven who are in Christ. Proof:
Acts 9:13,32,41; 26:10; 1 Cor. 6:1-2; 14:33; 2 Cor. 1:1; 8:4; 9:1-2; 13:13; Rom. 8:27; 12:23; 15:25,26, 31; 16:2,15; Eph. 1:1,15,18; 3:8; 5:3; 6:18; Phil. 1:1; 4:22; Col 1:2,4,26; 1 Tm 5:10; Philemon 1:5,7; Heb. 6:10; 13:24; Jude 1:3; Rev. 11:18; 13:7; 14:12; 16:6; 17:6;18:20,24; Rev 19:8; 20:9 - in these verses, we see that Christians still living on earth are called "saints."
Matt. 27:52; Eph. 2:19; 3:18; Col. 1:12; 2 Thess. 1:10; Rev. 5:8; 8:3-4; 11:18; 13:10 - in these verses, we also see that "saints" also refer to those in heaven who united with us.
Dan. 4:13,23; 8:23 – we also see that the angels in heaven are also called “saints.” The same Hebrew word “qaddiysh” (holy one) is applied to both humans and angels in heaven. Hence, there are angel saints in heaven and human saints in heaven and on earth. Loving beings (whether angels or saints) are concerned for other beings, and prayer is the spiritual way of expressing that love.
II. God Desires and Responds to Our Subordinate Mediation / Intercessory Prayer
1 Tim 2:1-2 - because Jesus Christ is the one mediator between God and man (1 Tim. 2:5), many Protestants deny the Catholic belief that the saints on earth and in heaven can mediate on our behalf. But before Paul's teaching about Jesus as the "one mediator," Paul urges supplications, prayers, intercessions, and thanksgivings be made for all people. Paul is thus appealing for mediation from others besides Christ, the one mediator. Why?
1 Tim 2:3 - because this subordinate mediation is good and acceptable to God our Savior. Because God is our Father and we are His children, God invites us to participate in Christ's role as mediator.
1 Tim. 2:5 - therefore, although Jesus Christ is the sole mediator between God and man, there are many intercessors (subordinate mediators).
1 Cor. 3:9 - God invites us to participate in Christ's work because we are God's "fellow workers" and one family in the body of Christ. God wants His children to participate. The phrase used to describe "fellow workers" is "sunergoi," which literally means synergists, or cooperators with God in salvific matters. Does God need fellow workers? Of course not, but this shows how much He, as Father, loves His children. God wants us to work with Him.
Mark 16:20 - this is another example of how the Lord "worked with them" ("sunergountos"). God cooperates with us. Out of His eternal love, He invites our participation.
Rom. 8:28 - God "works for good with" (the Greek is "sunergei eis agathon") those who love Him. We work as subordinate mediators.
2 Cor. 6:1 - "working together" (the Greek is "sunergountes") with him, don't accept His grace in vain. God allows us to participate in His work, not because He needs our help, but because He loves us and wants to exalt us in His Son. It is like the father who lets his child join him in carrying the groceries in the house. The father does not need help, but he invites the child to assist to raise up the child in dignity and love.
Heb. 12:1 - the “cloud of witnesses” (nephos marturon) that we are surrounded by is a great amphitheatre of witnesses to the earthly race, and they actively participate and cheer us (the runners) on, in our race to salvation.
1 Peter 2:5 - we are a holy priesthood, instructed to offer spiritual sacrifices to God. We are therefore subordinate priests to the Head Priest, but we are still priests who participate in Christ's work of redemption.
Rev. 1:6, 5:10 - Jesus made us a kingdom of priests for God. Priests intercede through Christ on behalf of God's people.
James 5:16; Proverbs 15:8, 29 - the prayers of the righteous (the saints) have powerful effects. This is why we ask for their prayers. How much more powerful are the saints’ prayers in heaven, in whom righteousness has been perfected.
1 Tim 2:5-6 - therefore, it is because Jesus Christ is the one mediator before God that we can be subordinate mediators. Jesus is the reason. The Catholic position thus gives Jesus the most glory. He does it all but loves us so much He desires our participation.
III. Specific Instructions to Mediate and Examples of Subordinate Mediation
New Testament
Matt. 5:44-45 - Jesus tells us to pray for (to mediate on behalf of) those who persecute us. God instructs us to mediate.
Matt. 17:1-3; Mark 9:4; Luke 9:30-31 – deceased Moses and Elijah appear at the Transfiguration to converse with Jesus in the presence of Peter, James and John (these may be the two “witnesses” John refers to in Rev. 11:3). Nothing in Scripture ever suggests that God abhors or cuts off communication between the living in heaven and the living on earth. To the contrary, God encourages communication within the communion of saints. Moses and Elijah’s appearance on earth also teach us that the saints in heaven have capabilities that far surpass our limitations on earth.
Matt. 26:53 – Jesus says He can call upon the assistance of twelve legions of angels. If Jesus said He could ask for the assistance of angel saints – and He obviously would not have been worshiping them in so doing – then so can we, who need their help infinitely more than Jesus, and without engaging in idolatry. And, in Matt. 22:30, Jesus says we will be “like angels in heaven.” This means human saints (like the angel saints) can be called upon to assist people on earth. God allows and encourages this interaction between his family members.
Matt. 27:47,49; Mark 15:35-36 – the people believe that Jesus calls on Elijah for his intercession, and waits to see if Elijah would come to save Jesus on the cross.
Matt. 27:52-53 - at Jesus' passion, many saints were raised and went into the city to appear and presumably interact with the people, just as Jesus did after His resurrection.
Mark 11:24 - Jesus says that whatever we ask in prayer, we will receive it. It is Jesus, and also we through Jesus, who mediate.
John 2:3 - Jesus knew the wine was gone, but invites and responds to Mary's intercession. God desires our lesser mediation and responds to it because He is a living and loving God.
John 2:5 - Mary intercedes on behalf of those at the wedding feast and tells them to do whatever Jesus tells them. Because Mary is our perfect model of faith, we too intercede on behalf of our brothers and sisters.
John 2:11 - in fact, it was Mary's intercession that started Jesus' ministry. His hour had not yet come, yet Jesus responds to Mary's intercession. Even though He could do it all by Himself, God wants to work with His children.
Acts 12:7 – an angel strikes Peter on the side and wakes him up, freeing him from prison. The angel responds to Peter’s prayers.
Rom. 15:30 - Paul commands the family of God to pray for him. If we are united together in the one body of Christ, we can help each other.
2 Cor. 1:11 - Paul even suggests that the more prayers and the more people who pray, the merrier! Prayer is even more effective when united with other's prayers.
2 Cor. 9:14 - Paul says that the earthly saints pray for the Corinthians. They are subordinate mediators in Christ.
2 Cor. 13:7,9 - Paul says the elders pray that the Corinthians may do right and improve. They participate in Christ's mediation.
Gal. 6:2,10 - Paul charges us to bear one another's burdens, and to do good to all, especially those in the household of faith.
Eph. 6:18 - Paul commands the family of God to pray for each other.
Eph. 6:19 - Paul commands that the Ephesians pray for him. If there is only one mediator, why would Paul ask for their prayers?
Phil. 1:19 - Paul acknowledges power of Philippians' earthly intercession. He will be delivered by their prayers and the Holy Spirit.
Col. 1:3 - Paul says that he and the elders pray for the Colossians. They are subordinate mediators in the body of Christ.
Col. 1:9 - Paul says that he and the elders have not ceased to pray for the Colossians, and that, by interceding, they may gain wisdom.
Col. 4:4 - Paul commands the Colossians to pray for the elders of the Church so that God may open a door for the word. Why doesn't Paul just leave it up to God? Because subordinate mediation is acceptable and pleasing to God, and brings about change in the world. This is as mysterious as the Incarnation, but it is true.
1 Thess. 5:11 - Paul charges us to encourage one another and build one another up, in the body of Christ. We do this as mediators in Christ.
1 Thess. 5:17 - Paul says "pray constantly." If Jesus' role as mediator does not apply subordinately to us, why pray at all?
1 Thess. 5:25 - Paul commands the family of God to pray for the elders of the Church. He desires our subordinate mediation.
2 Thess. 1:11 - Paul tells the family of God that he prays for us. We participate in Christ's mediation because Christ desires this.
2 Thess. 3:1 - Paul asks the Thessalonians to pray for Him, Silvanus and Timothy so that they may be delivered.
1 Tim. 2:1-3 - Paul commands us to pray for all. Paul also states that these prayers are acceptable in the sight of God.
2 Tim. 1:3 – Paul says “I remember you constantly in my prayers.”
Philemon 22 - Paul is hoping through Philemon's intercession that he may be able to be with Philemon.
Heb. 1:14 – the author writes, “Are they not all ministering spirits sent forth to serve, for the sake of those who are to obtain salvation?”
Hebrews 13:18-19 - the author strongly urges the Hebrews to pray for the elders so that they act desirably in all things.
James 5:14-15- James says the prayer of the priests over the sick man will save the sick man and forgive his sins. This is a powerful example of men forgiving sins and bringing a person to salvation with the sacrament of the sick.
James 5:16 - James instructs us to confess our sins to one another and pray for one another so that we may be healed.
James 5:17-18 - James refers to God's response to Elijah's fervent prayer for no rain. He is teaching us about the effectiveness of our earthly mediation.
1 John 5:14-15 - John is confident that God will grant us anything we ask of God according to His will.
1 John 5:16-17 - our prayers for others even calls God to give life to them and keep them from sinning. Our God is a personal and living God who responds to our prayers.
3 John 2 - John prays for Gaius' health and thus acts as a subordinate mediator.
Rev. 1:4 – this verse shows that angels (here, the seven spirits) give grace and peace. Because grace and peace only come from God, the angels are acting as mediators for God.
Rev. 5:8 - the prayers of the saints (on heaven and earth) are presented to God by the angels and saints in heaven. This shows that the saints intercede on our behalf before God, and it also demonstrates that our prayers on earth are united with their prayers in heaven. (The “24 elders” are said to refer to the people of God – perhaps the 12 tribes and 12 apostles - and the “four living creatures” are said to refer to the angels.)
Rev. 6:9-11 – the martyred saints in heaven cry out in a loud voice to God to avenge their blood “on those who dwell upon the earth.” These are “imprecatory prayers,” which are pleas for God’s judgment (see similar prayers in Psalm 35:1; 59:1-17; 139:19; Jer. 11:20; 15:15; 18:19; Zech.1:12-13). This means that the saints in heaven are praying for those on earth, and God answers their prayers (Rev. 8:1-5). We, therefore, ask for their intercession and protection.
Rev. 8:3-4 – in heaven an angel mingles incense with the prayers of all the saints on the golden altar before the throne of God, and the smoke of the incense rose with the prayers of the saints from the hand of the angel before God. These prayers “rise up” before God and elicit various kinds of earthly activity. God responds to his children’s requests, whether made by his children on earth or in heaven.
Old Testament
Gen. 20:17 - God responds to Abraham's intercession and heals Abimelech, and also his wife and slaves.
Gen. 27:29; Num. 24:9 - blessed be everyone who blesses you. If we bless others in prayer, we are also blessed.
Exodus 32:11-14, 30-34; 34:9; Num. 14:17-20; 21:7-9 - these are many examples of God's response to Moses' saintly intercession.
1 Sam. 12:23 - Samuel says that he would be sinning against God if he didn't continue to intercede for the people of Israel.
1 Sam. 28:7-20 – the deceased prophet Samuel appears and converses with Saul, which is confirmed by Sirach 46:13,20).
1 Sam. 28:7; 1 Chron. 10:13-14 - Saul practiced necromancy. He used a medium, not God, to seek the dead and was therefore condemned. Saul's practice is entirely at odds with the Catholic understanding of saintly mediation, where God is the source and channel of all communication, and who permits His children to participate in this power.
2 Chron. 30:27 - the prayers of the priests and Levites came before God's holy habitation in heaven and were answered.
Tobit 12:12,15 - angels place Tobit and Sarah's prayers before the Holy One. This teaches us that the angels are also our subordinate mediators. We pray to the angels to take up our prayers to God.
Job 42:7-9 - Job prayed for three friends in sin and God listened to Job as a result of these prayers.
Psalm 34:7 – the angel of the Lord delivers those who fear him.
Psalm 91:11 – God will give His angels charge of you, to guard you in all your ways.
Psalm 103:20-21; 148:1-2 – we praise the angels and ask for their assistance in doing God’s will.
Psalm 141:2 - David asks that his prayer be counted as incense before God. The prayers of the saints have powerful effects.
Isaiah 6:6-7 - an angel touches Isaiah's lips and declares that his sin is forgiven. The angel is a subordinate mediator of God who effects the forgiveness of sins on God’s behalf.
Jer. 7:16 - God acknowledges the people's ability to intercede, but refuses to answer due to the hardness of heart.
Jer. 15:1 – the Lord acknowledges the intercessory power of Moses and Samuel.
Jer. 37:3 - king Zedekiah sends messengers to ask Jeremiah to intercede for the people, that he might pray to God for them.
Jer. 42:1-6 - all the people of Israel went before Jeremiah asking for his intercession, that he would pray to the Lord for them.
Baruch 3:4 - Baruch asks the Lord to hear the prayers of the dead of Israel. They can intercede on behalf of the people of God.
Dan. 9:20-23 - Daniel intercedes on behalf of the people of Israel confessing both his sins and the sins of the people before God.
Zech. 1:12-13 - an angel intercedes for those in Judea and God responds favorably.
2 Macc. 15:12-16 – the high priest Onias and the prophet Jeremiah were deceased for centuries, and yet interact with the living Judas Maccabeas and pray for the holy people on earth.
IV. Veneration / Honor of the Saints
Matt. 18:10 - the angels in heaven always behold the face of God. We venerate them for their great dignity and union with God.
Matt. 15:4; Luke 18:20; Eph. 6:2-3 Exodus 20:12; Lev. 19:3; Deut. 5:16 - we are instructed to honor our father and mother.
Luke 1:28 - the angel Gabriel venerates Mary by declaring to her "Hail, full of grace." The heavenly angel honors the human Mary, for her perfection of grace exceeds that of the angels.
Romans 13:7 - we are to give honor where honor is due. When we honor God's children, we honor God Himself, for He is the source of all honor.
1 Cor. 4:16 - the most important form of veneration of the saints is "imitating" the saints, as Paul commands us to do.
1 Cor. 11:1 - again, Paul says, "Be imitators of me, as I am of Christ." The ultimate objective of veneration is imitation.
Phil. 2:25-29 - Paul teaches us to honor Epaprhoditus who almost died for the faith. How much more honor is owed to the saints that did die for the faith!
Phil. 3:17 - Paul says to imitate him and others, which is the goal of veneration. Veneration is not worship.
1 Thess. 1:6 – Paul says to the Thessalonians, “You became imitators of us and of the Lord.” This is the goal of veneration.
2 Thess. 3:7 - Paul says that the Thessalonians should imitate him and the other bishops.
Hebrews 3:3 - Jesus is worthy of "more" glory and honor than Moses. This does not mean that the saints are worthy of no glory and honor. Instead, it proves that saintly people are worthy of glory and honor out of God's goodness.
Heb. 6:12 – the author teaches us to be imitators of those who through faith and patience inherit the promises.
Heb. 13:7 - we must imitate the faith of our faithful leaders. We ask for their intercession and venerate them for their holiness.
James 5:10-11 – James teaches us to take heart in the examples of the prophets and Job, who endured suffering.
1 Peter 2:17 - Peter teaches us to honor all men, love the brotherhood, fear God, honor the emperor. Don't those living with Christ in heaven deserve honor? Catholics believe they do, and honor them with special feast days, just as we honor those living by celebrating their birthdays.
Gen. 19:1 - Lot venerates the two angels in Sodom, bowing himself with his face to the ground.
Gen. 42:6 - Joseph's brothers bow before Joseph with the face to the ground. This is veneration, not worship.
Exodus 28:2 - it is especially important to honor religious leaders. Sacred garments for Aaron give him dignity and honor.
Lev. 19:32- we should also honor "the face of an old man." When the elderly die in Christ, we should continue honoring them, because death does not separate them from us or the love of Christ.
1 Sam. 28:14 - Saul bows down before Samuel with his face to the ground in veneration.
2 Chron. 32:33 - Hezekiah was honored at his death. We honor our brothers and sisters in the Lord.
Sir. 44:1-2 - we should praise and give honor to those who the Lord apportioned great glory. It is our family in Christ.
V. Posture in Prayer, Veneration and Worship
Deut. 5:9 - God's command, "you shall not bow down to them" means "do not worship them." But not all bowing is worship. Here God's command is connected to false worship.
Rev. 3:9 - Jesus said people would bow down before the faithful members of the church of Philadelphia. This bowing before the faithful is not worship, just as kissing a picture of a family member is not worship.
Gen. 19:1 - Lot bowed down to the ground in veneration before two angels in Sodom.
Gen. 24:52 - Abraham's servant bowed himself to the earth before the Lord.
Gen. 42:6 - Joseph's brothers bow before Joseph with the face to the ground.
Jos. 5:14 - Joshua fell to the ground prostrate in veneration before an angel.
1 Sam. 28:14 - Saul bows down before Samuel with his face to the ground in honor and veneration.
1 Kings 1:23 - the prophet Nathan bows down before King David.
2 Kings 2:15 - the sons of the prophets bow down to Elisha at Jericho.
1 Chron. 21:21 - Ornan the Jebusite did obeisance to king David with his face to the ground.
1 Chron. 29:20 - Israelites bowed down to worship God and give honor to the king.
2 Chron. 29:29-30 - King Hezekiah and the assembly venerate the altar by bowing down in worship before the sin offerings.
Tobit 12:16 - Tobiah and Tobit fell down to the ground in veneration before the angel Raphael.
Judith 14:7 - Achior the Ammonite kneels before Judith venerating her and praising God.
Psalm 138:2 - David bows down before God's Holy Temple.
Dan. 2:46 - the king fell down on his face paying homage to Daniel and commands that an offering be made to him.
Dan. 8:17 - Daniel fell down prostrate in veneration before the angel Gabriel.
1 Macc. 4:40,55 - Judas and the faithful fell face down to the ground to praise heaven and worship God.
2 Macc. 10:4,26; 13:12 - Maccabeus and his followers fall down prostrate praying to God.