'Sackcloth' in the Bible

When the king heard the woman’s words, he tore his clothes. Then, as he was passing by on the wall, the people saw that there was sackcloth under his clothes next to his skin.

When King Hezekiah heard their report, he tore his clothes, covered himself with sackcloth, and went into the Lord’s temple.

Then he sent Eliakim, who was in charge of the palace, Shebna the court secretary, and the leading priests, who were wearing sackcloth, to the prophet Isaiah son of Amoz.