SACKCLOTH — coarse, dark goat-hair cloth, worn against the skin as the dress of mourning and repentance. It enters the Bible in this verse, on Jacob, as a father's response to a lie about his son (37:34), and stays: the king of Nineveh trades his robe for it (Jonah 3:6), and Revelation's two witnesses prophesy in it (Revelation 11:3). The English word 'sackcloth' is literal — the same rough stuff sacks were made of. → first discussed at Gen 37:34