Genesis 21:31-34

That place was called Beersheba, because it was there that both men swore an oath to one another. After completing their pact at Beersheba, King Abimelech and Phicol, his army commander, departed and returned to Philistine country. Abraham planted a tamarisk tree in Beersheba, and there he worshiped YAHWEH, the everlasting God. And Abraham lived many years in peace as a foreigner in Philistine country.