'Sackcloth' in the Bible

“Woe to you, Chorazin! Woe to you, Bethsaida! For if the miracles had occurred in Tyre and Sidon which occurred in you, they would have repented long ago in sackcloth and ashes.

“Woe to you, Chorazin! Woe to you, Bethsaida! For if the miracles had been performed in Tyre and Sidon which occurred in you, they would have repented long ago, sitting in sackcloth and ashes.

I looked when He broke the sixth seal, and there was a great earthquake; and the sun became black as sackcloth made of hair, and the whole moon became like blood;

And I will grant authority to my two witnesses, and they will prophesy for twelve hundred and sixty days, clothed in sackcloth.”