Abraham Calls Himself Dust and Ashes and Earns Two Commandments

"And Abraham answered and said, 'Behold now, I have undertaken to speak to the Lord, though I am but dust and ashes'" (Genesis 18:27). Rava expounded: As a reward for Abraham our father saying, "though I am but dust and ashes," his descendants merited two commandments: the dust of the suspected wife (sotah) and the ashes of the [red] heifer (parah). But is there not also the dust of covering [the blood of slaughter]? There, [the answer is,] there is the fitness for a commandment, but there is no benefit [derived].