Sackcloth was a rough material, often made from goat hair, used primarily as a symbol of mourning. Some prophets and captives also wore it.
Sackcloth was usually dark and coarse (Isaiah 50:3; Revelation 6:12). There are two main views about its shape.
Sackcloth was a rectangular garment, sewn on the sides and one end, with openings for the head and arms. This shape is similar to the grain sacks used by Joseph's brothers (Genesis 42:25–27, 35) and the sacks used by the Gibeonites (Joshua 9:4; compare Leviticus 11:32).
Sackcloth was more like a small loincloth. Hebrew practices support this. They include girding the loins with sackcloth (2 Samuel 3:31; Isaiah 15:3; 22:12; Jeremiah 4:8) and the placing of sackcloth on the loins (Genesis 37:34; 1 Kings 20:31; Jeremiah 48:37), though more than one type of garment could have been made from sackcloth.
Sackcloth was mainly associated with mourning (Genesis 37:34; 1 Kings 21:27; Lamentations 2:10). It was worn during national (2 Kings 6:30; Nehemiah 9:1; Isaiah 37:1; Jonah 3:8) as well as personal crises constituted times for the wearing of sackcloth. It was worn by:
Kings (1 Kings 21:27; 2 Kings 6:30)
Priests (Joel 1:13)
Elders (Lamentations 2:10)
Prophets (Isaiah 20:2; Zechariah 13:4)
It was worn by those who were repenting (Nehemiah 9:1; Jeremiah 6:26; compare Matthew 11:21). This practice was not limited to Israel (Isaiah 15:3; Jeremiah 49:3; Ezekiel 27:31; Jonah 3:5).
It has been suggested that the rough texture of sackcloth was uncomfortable and used to punish the wearer. However, there is no evidence to support this idea.