In Genesis 21:22-34, we see a much different Abraham. We see an Abraham that is confident in his faith, an Abraham who no longer deceives to achieve the ends God would have for him, and an Abraham who would rather make peace than go to war. And why shouldn't he be that way? Isaac, the child of promise, has been born. There is no longer any lingering doubt or uncertainty wrapped up in how the promises of God are going to come about. The threats to the promises have been removed, painful as it was. Hagar and Ishmael were sent away.
Given an opportunity to reclaim his reputation, Abraham is offered a treaty of peace from neighboring Abimelech. This is the same Abimelech from chapter twenty, the Abimelech Abraham deceived. It is interesting to note that the two key things Abimemelch knows about Abraham is that "God is with him" and that Abraham has dealt falsely in the past.
However, after the oaths are taken, Abraham discovers that Abimelech has dealt falsely with him. The army of Abimelech has seized control of Abraham's wells. Even today, water is a precious commodity in the ancient near east. This is a justifiable offense in that Abraham ought to go to war; he should go to war. However, Abraham, having met this Everlasting God (verse thirty-three), rather makes peace with Abimelech instead of going to war.
When you are offended by someone, is it your custom to go to war rather than make peace? Abraham had a formidable army; chapter fourteen showed us that. Abraham probably could have overwhelmed Abimelech's army (it is telling that the commander of Abimelech's army attended the ratification of their peace agreement in verse twenty-two). Abraham reflects the character of God in that when he was justified in making war, he chose to make peace instead.
(Taken from my sermon, A Good Neighbor, preached this past Sunday night)