Kommentar zu Bereschit 20:1

ויסע משם אברהם AND ABRAHAM JOURNEYED FROM THENCE—When he observed that the cities had been destroyed and travellers ceased to pass to and fro, he went away from there. Another explanation is: he journeyed from there to get away from Lot who had gained an evil reputation because of his intercourse with his daughters (Genesis Rabbah 52:3-4).

וישב בין קדש ובי שור, between 2 large cities, in order to have an opportunity to proclaim the holy name of G’d in both these cities, as he did later, the objective being to improve G’d’s image among mankind.

ויסע משם, from Eloney Mamre, the place where he resided most of the time. The Torah fails to mention what prompted Avraham to leave his home in this fashion. It could not have been due to the famine, seeing that at that time no famine is reported as having existed in that region, as opposed to when Yitzchok left his home and went to the land of the Philistines as reported in 26,1. Seeing that in that connection the Torah referred to this famine as being additional to the one in the days of Avraham, and we know that at that time Avraham went to Egypt and did not settle in the region between Kadesh and Shur, we cannot attribute his move to a famine. Perhaps what motivated Avraham was the need to fulfill the commandment by G’d to dwell in all parts of the land of Canaan. The Torah would indicate, obliquely, that the land of the Philistines was included in what G’d had described as “the land of Canaan,” even though the Philistines were distant descendants of Mitzrayim, a grandson of Cham but not directly descended from Canaan. Eventually, the coastal plain inhabited by the Philistines became part of the tribal territory of Yehudah. This may be why the Torah refers to this as ארצה הנגב, the southern region, seeing that Yehudah’s territory is described as the southern part of the country in Joshua chapter15.