'Dust on His Head' in the Bible

Now a man of Benjamin ran from the battle line and came to Shiloh the same day with his clothes torn and dust on his head.

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.