Берешит 13:11 Комментарий: Rashi, Chizkuni, Sforno & Kitzur Ba'al HaTurim

ככר The word means “a plain” as the Targum translates it.

ויפרדו איש מעל אחיו, “they separated totally from one another.” This separation lasted historically throughout the generations so that descendants (male) of Lot were never allowed to convert to Judaism. (Deuteronomy 23,4)

ויבחר לו לוט, he selected as much area as he himself with his shepherds would manage to control as their grazing land. In this section of the earth Avram and his shepherds would not be allowed to graze.

מקדם FROM THE EAST — He removed from Abram and went westward of Abram — consequently he travelled from the East to the West. A Midrashic explanation is: He wandered away from the Originator (מקדמונו) of the Universe, saying, “I want neither Abram nor his God” (Genesis Rabbah 41:7).