Genesis 21:14, 31-33

So Abraham rose early in the morning and took bread and a skin of water and gave it to Hagar, putting it on her shoulder, along with the child, and sent her away. And she departed and wandered in the wilderness of Beersheba.

Therefore that place was called Beersheba, because there both of them swore an oath. So they made a covenant at Beersheba. Then Abimelech and Phicol the commander of his army rose up and returned to the land of the Philistines. Abraham planted a tamarisk tree in Beersheba and called there on the name of the LORD, the Everlasting God.