Why did God institute a plan of redemption after the Fall?
Sin entered and separated Adam and Eve from God, removing them from the garden and breaking perfect fellowship. Because He had lost control of what He once owned, God instituted a plan of redemption to buy back and pay the price for that lost possession.
Les explains that redemption is a matter of buying back or paying the price for something God had once owned but lost. In the garden, God and Adam and Eve had perfect fellowship, but sin entered and separated them from God and out of the garden. So immediately God instituted a plan of redemption to buy back and pay the price for that which He had lost control of. The same pattern appears with Israel: because of sin, God lost control of His covenant people, and He would have to redeem them and pay the price to bring them back unto Himself.