And Abraham answered and said (being emboldened by the success of his first petition), Behold now, I have taken upon me, literally, I have begun, though here perhaps used in a more emphatic sense: I have undertaken or ventured—to speak unto the Lord—Adonai (Genesis 15:2)—which am but dust and ashes.
"Dust in his origin and ashes in his end" (Delitzsch; vide Genesis 3:19).