Genesis 21:22-31

At that time, King Abimelech and Phicol, his army commander, came to Abraham and said, “It is obvious that God is with you and blesses everything you do. Now swear to me here before God that you will not deceive me, my children, or my descendants, but as I have shown you loyal friendship, so you will treat me—and the land in which you live as a foreigner—with loyal friendship.” “I give you my oath,” Abraham answered. But Abraham voiced a complaint about a well of water which Abimelech’s servants had seized by force. Abimelech responded, “This is the first time I’ve heard about this; you never told me before now. I don’t know who has done this.” So Abraham took sheep and cattle, gave them to Abimelech, and the two men made a covenant. Then Abraham set apart from his flock seven ewe lambs, and Abimelech asked him, “What are you doing with these seven ewe lambs you have set apart?” He replied, “I am giving them to you, and by accepting these seven ewe lambs, you acknowledge the proof that I dug this well and it belongs to me.” That place was called Beersheba, because it was there that both men swore an oath to one another.