'Sackcloth' in the Bible

David said to Joab and to all the people who [were] with him, "Tear your clothing and put on sackcloth and mourn before Abner." Now King David [was] following after the bier.

Rizpah the daughter of Aiah took the sackcloth, and she spread it for herself on the rock at the beginning of the harvest until water gushed forth on them from heaven, but she did not allow the birds of heaven to rest on them by day nor the animals of the field by night.