וַיַּ֥עַן אַבְרָהָ֖ם וַיֹּאמַ֑ר הִנֵּה־נָ֤א הוֹאַ֙לְתִּי֙ לְדַבֵּ֣ר אֶל־אֲדֹנָ֔י וְאָנֹכִ֖י עָפָ֥ר וָאֵֽפֶר׃
And Abraham answered and said: ‘Behold now, I have taken upon me to speak unto the Lord, who am but dust and ashes.
Read kabbalistic (mystical) interpretation of Genesis 18:27: and classical mystical sources.