'Sackcloth' in the Bible

David then ordered Joab and all the people who were with him, “Tear your clothes, put on sackcloth, and mourn over Abner.” And King David walked behind the funeral procession.

Rizpah, Aiah’s daughter, took sackcloth and spread it out for herself on the rock from the beginning of the harvest until the rain poured down from heaven on the bodies. She kept the birds of the sky from them by day and the wild animals by night.