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.

Abraham planted a tamarisk tree at Beersheba, and there he called on the name of the LORD [in prayer], the Eternal God.