Genesis 26

Gen 26:28 They answered, "Now we know that the LORD is with you, and we think that there should be a solemn agreement between us. We want you to promise
Gen 26:29 that you will not harm us, just as we did not harm you. We were kind to you and let you go peacefully. Now it is clear that the LORD has blessed you."


God was Isaac’s ally and Abimilech knew that compared to the power of the Lord his army is no match against Him. So, rather than make Isaac an enemy, Abimilech deemed it better to make a treaty with him.

Rom 8:31 If God be for us, who can be against us?