'Sackcloth' in the Bible

So, put on sackcloth, mourn and wail, because the burning anger of the LORD has not turned away from us."

Daughter of my people, put on sackcloth and roll in ashes. Mourn with bitter wailing, as one mourns at the death of an only son. For the destroyer will come on us suddenly.

Indeed every head will be bald and every beard cut short. There will be gashes on all the hands and sackcloth on the loins.

"Wail, Heshbon, because Ai is destroyed. Cry out, daughters of Rabbah, put on sackcloth and lament. Run back and forth inside the walls, for Milcom is going into exile along with his priests and his princes.