Abraham is willing to sacrifice his son because it is part of God's will. Abraham does not fully understand God's will here but because he holds a covenant and is a follower of God, he consents. God's will is at least partially revealed to Abraham. Abraham recognizes that God wants to punish the sinful towns of Sodom and Gomorrah. While talking to Abraham God exclaims, "The outrage of Sodom and Gomorrah is so great, and their sin so grave!" (Genesis 18:20) God must punish the sinners for they have committed such grievous sins as rape and murder, and they because their existence jeopardizes the future of Abraham's "populous nation". (Genesis 18:18) God is being just and making sure there is a safe future for Abraham's descendants. Abraham understands that God is enacting justice upon he inhabitants of the towns. He is made aware of God's will when God decides "not to hide from Abraham what I [he] is about to do". (Genesis 18:17) Once Abraham realizes what God is about to do, his compassion for his fellow man rises up. Abraham can see that God is trying to carry out justice. This event closely parallel's God's decision to flood the earth. (Genesis 6:13-14) God is both punishing the townsfolk and also cleaning the slate. But here is where Abraham shows his compassion for his fellow righteous men. He has also been with God so long that he begins to understand God's character. Abraham points out to God that it is "Far be it from You [God] to do such a thing, to bring death upon the innocent as well as the guilty, so that the guilty fare alike". (Genesis 18:25) Abraham understands that this is not in God's nature, but God must do this in order for him to see his will out. Abraham is able to bargain with God because he is not directly involved in God's will here. God is not directing or commanding Abraham to do anything, as opposed to later in Genesis when God orders him to sacrifice his son.