Sin by definition is a violation of a commandment from God...technicially IF God commanded this..yes.
The only thing valid about your q is that sadly, there are people who have justified many murders claiming
righteousness or following what they claimed was justified from the Bible...when in fact, they've abused the Torah to do so.
Your examples fail to prove what you've claimed based upon several fallacies of extension and other misrepresentations though...some of them based upon later dogma from other religions...others upon misrepresentation out of context.
Abraham’s covenant was groundbreaking in the ancient world in that it was a rejection/separation from all the surrounding religions that relied on human sacrifice and beliefs that humans, (Pharaohs and other kings) could be incarnations or representations of gods in human form or deities outright. This narrative of Abraham and Isaac in its context teaches that the Creator who gave us life would never find it acceptable to kill our children to appease or seek atonement.Torah forever forbids human sacrifice and the consumption of any blood. Abraham’s covenant was groundbreaking in the ancient world in that it was a rejection/separation from all the surrounding religions that relied on human sacrifice and beliefs that humans, (Pharaohs and other kings) could be incarnations or representations of gods in human form or deities outright. This narrative of Abraham and Isaac in its context teaches that the Creator who gave us life would never find it acceptable to kill our children to appease or seek atonement. Another replacement theology tries to alter this story based upon the reference to his only son. Hagar and Ishmael were nowhere near Abraham in this narrative. The narrative has Hagar and Ishmael in exile. Ishmael was no longer considered by Abraham to be a son and he was not the son of his wife, but of a concubine, thus, never his heir according to the Torah and the promise of God to Abraham and Sarah.
Neither Yitzak (Isaac) or Ishmael were sacrificed according to the Torah. If God was showing that human sacrifice was acceptable, this was a very strange way to do it. God providing the ram indicated that his child was not an appropriate sacrifice. Abraham‘s dedication to do as God asked, despite Abraham‘s belief that it was wrong to sacrifice his child showed his complete trust in God, remember he told Isaac that God would provide the sacrifice. He trusted that God would not permit the death of the son whose heirs were to continue the eternal covenant promised.
I will run out of room showing how the other premises of your q are equally fallacious..for example...even when Jewish courts were in practice in the ancient Jewish kingdom, the execution of apostate Jews was not something performed except in the most extreme of circumstances and do you know why? Commandments from God in how to judge...
the death penalty was RARELY ever enacted. Any Jewish that enacted more than one execution in 70 years was considered cruel.
http://www.sacred-texts.com/jud/tsa/tsa14.htm < this is a place you can learn why the Jews rarely executed anyone, for any offense that could possibly result in death as a punishment for the offense.
Abraham told his servant waiting at the bottom of the mountain that he and the boy would return after sacrificing to God. This is said to reveal faith that God would not demand of him what he'd actually told him to do, that he already trusted that God would provide and spare this miracle child of his old age, promised to be the father of an eternal nation.
Another thing that jumped out at me the very first time I read this story as a child: He didn't mention a thing to Sarah, the woman who gave birth to the child in her old age. She was neither told or consulted when it came to the decision to offer her miracle child up as a human sacrifice. . How could God and Abraham do this..not say a THING to Sarah? Wasn't she the one to whom the miracle of his birth was given..doesn't she have any say in this? The story appears to indicate that right after this Abraham and Sarah separated.
19. And Abraham returned to his young men, and they arose and went together to Beer sheba; and Abraham remained in Beer sheba.
Note the next time Sarah is even mentioned.
And the life of Sarah was one hundred years and twenty years and seven years; [these were] the years of the life of Sarah.
2. And Sarah died in Kiriath arba, which is Hebron, in the land of Canaan, and Abraham came to eulogize Sarah and to bewail her.
( she didn't die in Beersheba, he had to come to her)
4. "I am a stranger and an inhabitant with you. Give me burial property with you, so that I may bury my dead from before me."
After the incident on the mountain with Isaac, Abraham returned to the servants he left below the mountain and with whom he left for Beersheba afterward. Nothing is mentioned of telling, asking or consulting Sarah or telling her they would return, nor is there mention that Abraham and Sarah were EVER together again until her burial!
As a mother,I think the whole incident was just too much for Sarah! Abraham did not question God about wanting the life of his very own son, yet he had challenged God over the destruction of strangers at Sodom and Gomorrah..this was viewed as a failure on his part to do what he should have done. It isn't forbidden to question God. Isaac's son Jacob's struggle with the messenger of God gave us the very name of our covenant nation, Israel, struggle with God..we strive toward a path of righteousness, testing and questioning to make sure what we follow is valid and is honoring our obligations given to us by God in the eternal covenant.
Abraham didn't just have children with Hagar and Sarah, and he didn't just have two sons, he also had Zimran, Jokshan, Medan Midian, Ishbak, and Shuah as recorded in Genesis chapter 25.
Not one of them were members of the covenant between God and Abraham.
God established the eternal covenant with Abraham and promised to continue it eternally through his progeny through Sarah, and all who joined them in affirmation and dedication to the path of instruction God gave for all the Yehudim. The word Jew comes from the Hebrew word Yehudi meaning to praise God. The angels visited Sarah to promise that her son would pass the covenant.
If God had wanted Isaac dead, how could the covenant have then been passed though him until today?
Murder is forbidden by commandment from God. Israel trusts that God does not violate the commandments given to us, nor expect us to violate them.
Killing in self defense is not considered murder..the instances of Israel killing off any people in the context of the narrative are in defense of their own existence. Don't forget about all the nation peoples ( tribal entties etc) that the Israelites encountered that they peacefully passed through and co-existed with who did not try to exterminate them that are also mentioned in the Torah.
Abraham's words to his servant he left at the bottom of the mountain and his words to Isaac showed him that HIS conscience told him that he knew God would not permit him to murder his child. So, that destroys the premise of your q even without going into any further detail as I did that destroyed a few others.
edit: Robert's answer is a great one. If anyone ever hears a voice saying to go kill a child ( OR ANYONE ELSE) and you think it's God telling you to do this..please check yourself into the nearest psychiatric facility for a complete work up.
if there had been mental health facilities in Abraham's day...I would have advised him to do the same. .....of course he knew he wouldn't have to kill Isaac..but the very idea that he'd be preparing his son for a sacrifice would have had Sarah sending a truck with men in white to put him in a straightjacket and cart him away if that had been an option and if she'd have known is something I don't doubt for a moment.