'Dust' in the Bible

On the third day, behold, a man came out of the camp from Saul, with his clothes torn and dust on his head. And it came about when he came to David that he fell to the ground and prostrated himself.

It happened as David was coming to the summit, where God was worshiped, that behold, Hushai the Archite met him with his coat torn and dust on his head.

So David and his men went on the way; and Shimei went along on the hillside parallel with him and as he went he cursed and cast stones and threw dust at him.

“Then I pulverized them as the dust of the earth;I crushed and stamped them as the mire of the streets.