Why did Avraham add that he was "dust and ashes"?
Rashi, Da'as Zekenim and Riva: He pointed out that he would have been turned into dust by the four kings, and into ashes by Nimrod (in Ur Kasdim), had Hashem not saved him.
Targum Yonasan: This was an expression of humility, in that Avraham considered himself as insignificant as dust and ashes. 1 .
Seforno: Avraham was actually apologizing for his audacity in querying Hashem, explaining that He failed to grasp Hashem's ways because he was merely dust and ashes.
Chulin, 89a: Hashem desires Yisrael, because even when He showers them with greatness, they take their cue from their father Avraham - whom Hashem made great, yet he declared ?ve?Anochi Afar va?Eifer!? - and make themselves small before Him. 2
Chulin 89a: Like Moshe and Aharon, who described themselves as ?nothing?- in Sh?mos 16:7, and David ha'Melech, who compared himself to a worm ? See Tehilim 22:7.
See Torah Temimah, note 43.