'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 a man came [unexpectedly] from Saul’s camp with his clothes torn and dust on his head [as in mourning]. When he came to David, he bowed to the ground and lay himself face down [in an act of great respect and submission].

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.

Now when Mordecai saw what was done, pulling off his robe, he put on haircloth, with dust on his head, and went out into the middle of the town, crying out with a loud and bitter cry.