'Sackcloth' in the Bible

"Woe to you, Chorazin! Woe to you, Bethsaida! For if the mighty works had been done in Tyre and Sidon which were done in you, they would have repented long ago in sackcloth and ashes.

"Woe to you, Chorazin! Woe to you, Bethsaida! For if the mighty works had been done in Tyre and Sidon which were done in you, they would have repented long ago, sitting in sackcloth and ashes.

I saw when he opened the sixth seal, and there was a great earthquake. The sun became black as sackcloth made of hair, and the whole moon became as blood.

I will give power to my two witnesses, and they will prophesy one thousand two hundred sixty days, clothed in sackcloth."