The verses that contain dust and ashes:
Genesis 18:27 - "And Abraham answered and said, Behold now, I have taken upon me to speak unto the LORD, which am but dust and ashes:"
Job 30:19 - "He hath cast me into the mire, and I am become like dust and ashes."
The verses that contain dust only:
Genesis 3:19 - "In the sweat of thy face shalt thou eat bread, till thou return unto the ground; for out of it wast thou taken: for dust thou art, and unto dust shalt thou return."
Ecclesiastes 3:20 - "All go unto one place; all are of the dust, all turn to dust again."
Let me add:
Ecclesiastes 12:7 - "Then shall the dust return to the earth as it was: and the spirit shall return unto God who gave it."