'Haircloth' in the Bible

Then the king, hearing what the woman said, took his robes in his hands, violently parting them; and, while he was walking on the wall, the people, looking, saw that under his robe he had haircloth on his flesh.

And on hearing it, King Hezekiah took off his robe, and put on haircloth, and went into the house of the Lord.

And he sent Eliakim, who was over the house, and Shebna the scribe, and the chief priests, dressed in haircloth, to Isaiah the prophet, the son of Amoz.