'Dust' in the Bible

On the third day a man with torn clothes and dust on his head came from Saul’s camp. When he came to David, he fell to the ground and paid homage.

When David came to the summit where he used to worship God, Hushai the Archite was there to meet him with his robe torn and dust on his head.

I pulverize them like dust of the earth;I crush them and trample them like mud in the streets.