'Sackcloth' in the Bible

And the people of Nineveh believed in God, and they proclaimed a fast and put on sackcloth--from the greatest of them {to the least important}.

And the news reached the king of Nineveh, and he rose from his throne and removed his royal robe, put on sackcloth, and sat in the ashes.

And [the] human beings and [the] animals must be covered [with] sackcloth! And they must call forcefully to God, and each must turn from his evil way and from the violence that is in his hands.