'Sackcloth' in the Bible

David said to Joab, and to all the people who were with him, Tear your clothes, and clothe yourselves with sackcloth, and mourn before Abner. King David followed the bier.

Rizpah the daughter of Aiah took sackcloth, and spread it for her on the rock, from the beginning of harvest until water was poured on them from the sky. She allowed neither the birds of the sky to rest on them by day, nor the animals of the field by night.