The price of sin was death, both physical and spiritual, eternal separation from God. But God had no intention of losing us forever, He had a plan. Life is in the blood and blood would be spilled, a death had to occur to atone for sin, God would allow a sacrifice to take our place. In the Old Testament of the Bible God set up a system of sacrifice in which animals were killed, their blood was spilled to take the place of the spiritual death of men. This was just a representation of the perfect sacrifice that was yet to come, it could not gain people entrance into Heaven. Until the blood of the perfect sacrifice was shed the people who died in faith and obeyed the laws of the sacrifice were taken to a place called Abraham's Bosom or Paradise. Luke 16:20-31 is the story of two men who died, a rich man and Lazarus, a beggar. The rich man went to hell but Lazarus was taken by angels into Abraham's Bosom. The tormented rich man wanted Lazarus to give him a drop of water but was told by Abraham that there was a great gulf fixed between the two places making it impossible to pass from one place to the other. Paradise was not Heaven, it was an underworld place adjacent to Hell. But Paradise was not to be the eternal abode of the righteous, one day God's perfect sacrifice would bring them out of there, and take them to Heaven.
"But when the time had fully come, God sent His son to be born of a woman and born under the law, to purchase back those that were under the (imperfect) law, that we might receive the adoption of sons." Gal. 4:4-5 KJV paraphrased.
Jesus Christ, God made flesh, was born for one reason, to become the perfect, unblemished, sinless sacrifice for our sins. When He died on the cross he took our place so that we could again be sons and daughters of God and live forever with Him.
This is my own thought, I've never heard it in a sermon by anyone or read it in a book, but I think of the Tree of the Knowledge of Good and Evil as a type or representation of Christ and his death on the cross, when Adam and Eve took from the tree and ate of it, they took what was perfect and made it imperfect and received in themselves the curses of sin and death. The Lord was not evil or sinful but He knew about evil and sin and they also received that knowledge. When Jesus died on the cross it was as if the perfect fruit was placed back on the tree and took all sin and evil back into himself and destroyed it in the lives of those who accept His sacrifice for them.
This is a link to a site where you can look up scripture references in many different versions of the bible: http://www.biblegateway.com/