Rashi on Genesis 13:14/רש"י על בראשית י״ג:י״ד

1אחרי הפרד לוט AFTER LOT WAS SEPARATED FROM HIM — So long as the wicked (Lot) was with him the word of God kept away from him (i. e. God had no communion with Abraham) (Midrash Tanchuma, Vayetzei 10).