Genesis 26:33

He called it Shebah. Isaac’s servants informed him of their success in opening a new well that very day, and to it he gave the name of Shebah, meaning “oath,” in commemoration of the treaty with Abimelech. The statement, “therefore the name of the city is called Beer-sheba,” does not discredit the fact that Abraham had already given that very name to the place (Genesis 21:31). There was now an added reason for perpetuating the name assigned the spot a century earlier. As the treaty between Abimelech and Isaac was but a renewal of the earlier treaty, so the name Shebah given by Isaac to the new well was a reaffirmation of the earlier name, Beersheba.