"I have begun to speak to my Lord although I am (Anochi) but dust and ash." (Genesis 18:27)
Rashi cites the Midrash that the words “dust and ash” in this verse refer to two events that happened to Avraham Aveinu.
He was fit to become dust (ie. die) in the battle of the Four Kings vs. Five Kings, and but for Hashem’s mercy he could have become ash when Nimrod had thrown him into the fiery furnace for professing belief in the One G-d.
While this is a beautiful explanation, something seems amiss with the verb tense.
Rashi’s explanation focuses on what could have happened to Avraham in the past … yet in the verse we find that Avraham uses the word Anochi (“I am”) which speaks in present tense!
It would appear that “I was but dust and ash” might have been a more appropriate form to express the idea of the Midrash.
Yalkut Lekach Tov explains that there is a lesson in Hakaras HaTov (gratitude) to be learned here:
An average expression of gratitude will thank someone for what was done for him in the past. However, the Torah view is that we must also acknowledge that everything good that will come in the future also flows from that event too!
And so here, Avraham isn’t just giving thanks for what happened in the past – that he could have been killed in the war or by Nimrod – but he is currently living with the same feelings of gratitude.
He knows that but for Hashem’s kindness to him at those earlier times, none of the later blessings and triumphs would be possible. And for that, he expresses himself with the term Anochi (“I am”).