Sackcloth

Sackcloth (Hebrew: שַׂק śaq) is a coarsely woven fabric, usually made of goat's hair. The term in English often connotes the biblical usage, where the Hastings' Dictionary of the Bible remarks that haircloth would be more appropriate rendering of the Hebrew meaning.

In some Christian traditions (notably Catholicism), the wearing of hairshirts continues as a self-imposed means of mortifying the flesh that is often practiced during the Christian penitential season of Lent, especially on Ash Wednesday, Good Friday, and other Fridays of the Lenten season.