Genesis 18:27
25 Far be it from you to do such a thing—to kill the godly with the wicked, treating the godly and the wicked alike! Far be it from you! Will not the judge of the whole earth do what is right?” 26 So the Lord replied, “If I find in the city of Sodom 50 godly people, I will spare the whole place for their sake.” 27 Then Abraham asked, “Since I have undertaken to speak to the Lord (although I am but dust and ashes), 28 what if there are five less than the 50 godly people? Will you destroy the whole city because five are lacking?” He replied, “I will not destroy it if I find 45 there.” 29 Abraham spoke to him again, “What if 40 are found there?” He replied, “I will not do it for the sake of the 40.”
Job 42:6
4 You said, ‘Pay attention, and I will speak; I will question you, and you will answer me.’ 5 I had heard of you by the hearing of the ear, but now my eye has seen you. 6 Therefore I despise myself, and I repent in dust and ashes!” 7 After the Lord had spoken these things to Job, he said to Eliphaz the Temanite, “My anger is stirred up against you and your two friends because you have not spoken about me what is right, as my servant Job has. 8 So now take seven bulls and seven rams and go to my servant Job and offer a burnt offering for yourselves. And my servant Job will intercede for you, and I will respect him, so that I do not deal with you according to your folly, because you have not spoken about me what is right, as my servant Job has.”
Notes and References
"... When it comes to the interpretation of רפאו רפע־לע יתמחנו, I follow de Wilde ... The expression (“dust and ashes/dirt”) occurs only in Genesis 18:27; Job 30:19b; 42:6b; Sirach 10:9 (Ms A); and Sirach 40:3 (Ms B). See also Sirach 17:32b (LXX). In Genesis 18:27 Abraham humbly says to God (“I am dust and ashes”) when he pleads in Sodom’s defense. In Job 30:19b Job points out that he is at death’s door: (“and I have become like dust and ashes”). This means that it refers to the physical constitution of a human being, more particularly to his/her condition sub specie aeternitatis (Genesis 18:27), his/her frailty and transitoriness (Job 30:19). This interpretation is confirmed by Sirach 10:9 (Ms A): “why are dust and ashes proud // even during life his intestines are putrefied”; and Sirach 17:32b (LXX): “and all men are dust and ashes”. It is also in accordance with the translation of the LXX of Job 42:6: “I consider myself dust and ashes”; in the same vein 11QtgJob (“and I am become dust and ashes”). And finally, it is in accordance with the traditional Targum: םטקו ארפע ןוניהד יינבמ (“for my children who are dust and ashes”). Otherwise, only Sirach 40:3 (Ms B): “from him who sits on a throne in pride // to him who is humiliated in dust and ashes ..."
van der Lugt, Pieter Who Changes His Mind about Dust and Ashes? The Rhetorical Structure of Job 42:2-6 (pp. 623-639) Vetus Testamentum 64, 2014