Genesis 21:31-33 New English Translation (NET Bible)
31 That is why he named that place Beer Sheba, because the two of them swore an oath there.
32 So they made a treaty at Beer Sheba. Then Abimelech and Phicol, the commander of his army, returned to the land of the Philistines. 33 Abraham planted a tamarisk tree in Beer Sheba. There he worshiped the Lord, the eternal God.