Genesis 21:14, 31-33

So Abraham got up early in the morning and took bread and a skin of water and gave them to Hagar, putting them on her shoulder, and gave her the boy, and sent her away. And she left [but lost her way] and wandered [aimlessly] in the Wilderness of Beersheba.

Therefore that place was called Beersheba (Well of the Oath or Well of the Seven), because there the two of them swore an oath. So they made a covenant at Beersheba; then Abimelech and Phicol, the commander of his army, got up 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 [in prayer], the Eternal God.