Charles Ellicott Commentary Genesis 26:33

"And he called it Shibah. Therefore the name of the city is Beer-sheba unto this day." — Genesis 26:33 (ASV)

Therefore the name of the city is Beer-sheba unto this day. —There was no city at this time at Beer-sheba, but one is mentioned at the conquest of Canaan by Joshua (Joshua 15:28). This note, as is the case generally with those which speak of a thing existing "unto this day," was added by Ezra and the men of the Great Synagogue after the return from Babylon . Its meaning is that whereas Abraham’s name had been forgotten while the place lay desolate, this remarkable coincidence of the water being found again, just when the covenant had been confirmed by the customary sevenfold sacrifice, so impressed the minds of the people that the title of Beer-sheba never again passed into oblivion.