Sackcloth

Sackcloth (Hebrew שַׂק saḳ) is a term originally denoting a coarsely woven fabric, usually made of goat's hair. It later came to mean also a garment made from such cloth, which was chiefly worn as a token of mourning by the Israelites. It was furthermore a sign of submission (I Kings xx. 30 et seq.), and was occasionally worn by the Prophets.