I Am Dirt

Avrohom in his prayers to spare the towns of Sedom said "I am dirt and ashes."  Chazal (Chullin 89b) say that for these words Avrohom was rewarded with the mitzvot of afar parah adumah and afer soteh.  Why are these mitzvot the reward for this statement?

The Meshech Chochma explains that natural growing things such as plants are not susceptible to accept tumah.  It is only where there is the work of man involved that things become susceptible to accept tumah.  We see from here that naturally things are pure, it is human involvement that makes things fitting to accept tumah.  The Avos became "purified" by negating their own ego, their own feeling of self before Hashem. This is reflected in the statement of Avrohom where he says he is" dirt and ashes."  By nullifying himself before Hashem, Avrohom was able to purify himself from the "poison" that was put into mankind by the sin of the aitz haddas.  The dirt used in the process of checking a sotah allows the woman to become pure (sotah is called tameh,) and return to her husband.  Similarly, the ashes of the parah adumah are used to make a person tahor and Hashem.  Since Avrohom returned to his natural state of earth and became purified, therefore he merited to receive mitzvot of purity.

The Maharal has a similar approach.  His focus is on that earth is where man comes from and its returning to the original, pure source that effects purity.  Similarly, through afer sotah a woman returns to her husband and a person returns to a state of purity through afer parah adumah. I would add to this what the Maharal writes in Netzach Yisroel (chapter 57) that earth is element that is the basis of everything; the ultimate returning to the source is to feel that one is reduces to his/her most basic element of earth.  

It is interesting that Avrohom doesn't say "I am dirt and ashes" as a preamble to his first prayer, only when continuing to beseech for a second time to save Sedom does he start off with this statement of humility.  Why does he only express it in the second prayer and not in the first?  Rav Dovid Solevetchik suggests that the first prayer of Avrohom was one that was al pi din as Avrohom said "how could God not be just."  The additional prayers were asking to save lifnim m'shuras hadin and for that Avrohom had to say I have no zechus to be listened too, I'm asking lifnim m'shuras hadin.  

I would like to suggest a different approach.  The first request of Avrohom was prayer that was fine.  However, to continue to beseech God is dangerous.  Unless one is sure that his intentions are completely pure and for the sake of the honor of Hashem, excessive prayer wouldn't be allowed for it would be second guessing God's judgement.  It's only allowed if one is confident that his/her prayer is merely leshem shamayim. I think that the intro. of Avrohom wasn't part of his prayer, it was a physiological test to see if he had any outside feelings that were encouraging him to continue praying.  If he had any feelings other than kovod shamayim he wouldn't be able to say "I am dirt and ashes."  Only after Avrohom guaranteed himself that his intentions were completely leshem shamayim was he able to continue praying without concern of second guessing God.