'Sackcloth' in the Bible

When the king heard the woman’s words, he tore his clothes—now he was still walking along on the wall—and the people looked [at him], and he had on sackcloth underneath [his royal robe] next to his skin.

When king Hezekiah heard it, he tore his clothes and he covered himself with sackcloth and went into the house (temple) of the Lord.

Then he sent Eliakim who was in charge of his household, Shebna the scribe, and the elders of the priests, covered with sackcloth, to Isaiah the prophet the son of Amoz.