Rashi on Genesis 25:18/רש"י על בראשית כ״ה:י״ח

1נפל (literally, he fell) means ‘‘he dwelt”, as (Judges 7:12) “Now the Midianites and the Amalekites and all children of the East dwelt (נופלים) in the valley.” Here it says “He fell” and there (16:12) it says “In the presence of all his brethren shall he dwell”. But it may be explained thus: before Abraham died it could be said “He would dwell in security: after he died, “he fell” (Genesis Rabbah 62:5).