In Job 2:12, when Job's friends first see Job at a distance, they "did not recognize him, and they raised their voices, and wept aloud; they tore their robes and threw dust in the air upon their heads."
I know that tearing of one's clothes is a common mourning ritual as portrayed throughout the Bible, but is throwing dusts upon one's head as well?
Where did the mourning ritual of throwing dusts on one's self originate? What is is symbolic of? What other accounts do we have in the Bible for it?
Is this mourning ritual still performed by some sects of Judaism today?