Genesis 21:22-34 NIV
At that time Abimelek and Phicol the commander of his forces said to Abraham, “God is with you in everything you do. Now swear to me here before God that you will not deal falsely with me or my children or my descendants. Show to me and the country where you now reside as a foreigner the same kindness I have shown to you.”
Abraham said, “I swear it.”
Then Abraham complained to Abimelek about a well of water that Abimelek’s servants had seized. But Abimelek said, “I don’t know who has done this. You did not tell me, and I heard about it only today.”
So Abraham brought sheep and cattle and gave them to Abimelek, and the two men made a treaty. Abraham set apart seven ewe lambs from the flock, and Abimelek asked Abraham, “What is the meaning of these seven ewe lambs you have set apart by themselves?”
He replied, “Accept these seven lambs from my hand as a witness that I dug this well.”
So that place was called Beersheba, because the two men swore an oath there.
After the treaty had been made at Beersheba, Abimelek and Phicol the commander of his forces returned to the land of the Philistines. Abraham planted a tamarisk tree in Beersheba, and there he called on the name of the LORD, the Eternal God. And Abraham stayed in the land of the Philistines for a long time.
NIV: New International Version