'Haircloth' in the Bible

And David said to Joab and all the people who were with him, Go in grief and put haircloth about you, in sorrow for Abner. And King David went after the dead body.

And Rizpah, the daughter of Aiah, took haircloth, placing it on the rock as a bed for herself, from the start of the grain-cutting till rain came down on them from heaven; and she did not let the birds of the air come near them by day, or the beasts of the field by night.