Jonathan, please do. I don't see how bible scriptures could say anything about the history of determining death. And this is the theology most Christians teach.
Alright. I currently do not have the time to sit down and gather scriptures to support what I'm putting forward, but I will provide them as soon as I am able.
In the Old Testament, it was always understood that blood being spilled was offering atonement for sins. On the day of atonement each year, Israel took sacrifices to the priest for atonement and that animals blood was spilled and the life offered to God in asking for forgiveness of sins. Somewhere in Hebrews (I believe) Paul calls the law, "Faulty." He calls it so because it could NEVER fully atone for the original sin, and this is obvious because it needed to be repeated yearly. So these two points need to be remembers going forward:
1. Only blood (life) offered to God atoned for sin in any significant way (I.e., Cains sacrifice was worth less than Abels).
2. No blood (life) offered to God could ever atone completely for mankinds sin. No animal is equal to imperfect man, let alone sinlessness (which was lost).
Having established the above, we move into the New Testament. It would be more proper to view John 3:16 not as saying God, "gave" but rather than he, "gave permission" or, "allowed." The scriptures state that Christ, "humbled himself and took a slaves form" from his pre-human, heavenly life to his human PERFECT state. This indicates very clearly it was his free choice to do this, and that is the most significant point to remember about the story. God did not FORCE Jesus to do this, Jesus humbled himself of his own free will and his Father (Almighty God) gave permission or allowed it.
I believe 2 Peter 2:1...? Calls Christ our, "owner." This is because he CHOSE to repurchase us, which follows an ancient custom of the repurchaser. You see an example of this in the book of Ruth. So what actually happened is as follows:
Christ willingly, of his own free will, became a man and used his sinless blood (life) to completely atone in one payment for our sinful state in a transaction (of sorts) in which he literally buys mankind back from sin. Thus he atoned perfectly for all sin past, present, and future - nullifying the mosaic law because further atonement would never be necessary.
As a REWARD for his willful and loving deed, he was not left in the grave but raised to be king over mankind whom he now owned and rightfully rules. His perfect blood being spilled was a one time transaction which, once complete, accomplished fully the repurchasing of man. Thus it was necessary for him to die in order for us to have hope, and it was unnecessary for him to stay dead. If he had stayed on the earth eternally, and his blood never been offered, we would have no hope at all and would be eternally subject to sin, pain, and death.
Further, Kaik's comment is wrong in every way - no offense meant. But the Jews always had a mediator. The role was taken by the high priest at the temple, who mediated between them and God by over seeing the sacrifice.
second Christ is not 1/3rd of God. Even the trinity, if you believe, firmly asserts them as separate beings with the almighty at the head as superior to all. They make up a family, not all one person. Further the trinity is demonstrably wrong, as Hebrews 1 shows Christ with authority over all the angels, having been risen above them to the point of being worshipped - nothing is above him except God Almighty himself. Yet, Christ knew in John 14 he would have no authority over the Holy Spirit but would have to petition the Father to send it. Hence the Holy Spirit cannot be an angel because if it were Christ would be its authority and he is not.