'Sackcloth' in the Bible

For this clothe yourself with sackcloth, lament and wail; for the fierce anger of Yahweh hasn't turned back from us.

Daughter of my people, clothe yourself with sackcloth, and wallow in ashes! Mourn, as for an only son, most bitter lamentation; for the destroyer shall suddenly come on us.

For every head is bald, and every beard clipped: on all the hands are cuttings, and on the waist sackcloth.

Wail, Heshbon, for Ai is laid waste; cry, you daughters of Rabbah, clothe yourself in sackcloth: lament, and run back and forth among the fences; for Malcam shall go into captivity, his priests and his princes together.