dear friend-- iam very happy to answer the questions which you asking . this is very important one among them.
agni sakshi - "Fire as the witness."
Homam, fire ritual, do not form a part of the main function in South Indian weddings. In brahmin communities fire rituals like nagavalli & lAja homam are performed only after the mangalyadaarana ceremony. Ancestors are the witness to the main wedding, not the fire God.
After the main ceremony, the holy fire is lit symbolizing purity and serving as a witness to the vows that are to follow. The couple offers prayers to Agni (the God of Fire). These prayers have a special significance for the couple who say, "Today in your presence, we have become one, and only you can separate us from one another." The Bride and Groom will make an offering of rice into the Agni, which symbolizes fertility, friendship, and the good fortune of their marriage. It is believed that Agni will dispel darkness and ignorance from the couple’s life and lead them into the world of light and knowledge.
nagavalli---
An important post marriage ritual performed on the wedding day is nAgavalli. saptapadi, the seven steps & the vows, form part of nagavalli. The bride and groom pledge and declare to all those present that they have accepted one another voluntarily. Holding each other's hands, the couple takes seven steps, symbolic of the seven marital vows, around the sacred fire.
As they hold hands and walk around the fire, the bride and groom pledge the following vows:
1. Let us take this first step vowing to keep a pure household, avoiding all things injurious to our health.
2. Let us take this second step vowing to develop mental, physical and spiritual strengths.
3. Let us take this third step with the aim of increasing our wealth by righteous means.
4. Let us take this fourth step to acquire knowledge, happiness, and harmony by mutual love and trust.
5. Let us take this fifth step to pray for virtuous, intelligent and courageous children.
6. Let us take this sixth step for longevity.
7. Let us take this final step to vow that we will always remain true companions and life-long partners.
This is a very significant event in the whole marriage ceremony, and it is only when they walk seven steps together, that the marriage is complete legally according to the vedic hindu scriptures.
During nagavalli, a silk cloth cradle was made and a piece of sandalwood, a ripe mango and turmeric was placed in it to pray for an off spring as healthy as the ripe mango, as pure as the turmeric and as self fragrant as the sandalwood. This is followed by a fun filled event where the bride and groom fight over who will collect the gold and silver rings dropped in a narrow mouthed vessel. Probably to check who dominates in the new family.
Holding the bride’s left foot toe, the bridegroom then helps her tread on a grindstone called sannikallu kept on the side of the fire. The manthras say: "Mount up this stone. Let thy mind be rock-firm, unperturbed, by the trials and tribulations of life" and when it is finished, the groom adorns the bride's toes with mettelu, silver rings. At this time the priest shows the couple the Arundhati star. Arundhati, the wife of vasisTha maharshi(the great saint), is exemplified as an ideal wife, the embodiment of chastity. By seeking her blessings, the bride expresses her devotion toward family life.
This is followed by appagintalu the official handover of the bride to the groom and ever since her family name is renamed.
thanq very much for giving the opputunity to answer your excellent question.