'Sackcloth' in the Bible

Because of this gird yourselves [with] sackcloth, lament and wail, for {the burning anger} of Yahweh has not turned back from us.

O daughter of my people, gird yourself [with] sackcloth, and roll about in the ashes in mourning, a mourning ceremony [as for] an only child. Make for yourself wailing of bitterness, for suddenly the destroyer will come upon us.

For [on] every head [is] baldness, and every beard is trimmed. On all [the] hands, slashes, and on [the] loins, sackcloth.

"Wail, Heshbon, for Ai is devastated. Cry out, O daughters of Rabbah, put on sackcloth. Lament and run back and forth among the walls. For Milcom will go into exile, his priests and his officials together.