C. F. Keil and Franz Delitzsch on Genesis 12:8-9

Gen 12:8-9

He did this also in the mountains, to which he probably removed to secure the necessary pasture for his flocks, after he had pitched his tent there. “Bethel westwards and Ai eastwards,” i.e., in a spot with Ai to the east and Bethel to the west. The name Bethel occurs here proleptically: at the time referred to, it was still called Luz (Gen 28:19); its present name if Beitin (Robinson's Palestine). At a distance of about five miles to the east was Ai, ruins of which are still to be seen, bearing the name of Medinet Gai (Ritter’s Erdkunde). On the words “called upon the name of the Lord,” see Gen 4:26. From this point Abram proceeded slowly to the Negeb, i.e., to the southern district of Canaan towards the Arabian desert (vid., Gen 20:1).