Sforno on Genesis 13:9/ספורנו על בראשית י״ג:ט׳

1הלא כל הארץ לפניך, I’ll let you choose the area which you prefer.

2Therefore, הפרד נא מעלי, move away from me in the direction you prefer and I will move in the opposite direction. If you select grazing land to the left, I will select grazing land to the right.