Genesis 21:31-34

Therefore he called that place Beersheba, because there the two of them took an oath. So they made a covenant at Beersheba; and Abimelech and Phicol, the commander of his army, arose and returned to the land of the Philistines. Abraham planted a tamarisk tree at Beersheba, and there he called on the name of the LORD, the Everlasting God. And Abraham sojourned in the land of the Philistines for many days.