'Sackcloth' in the Bible

And it shall come to pass, that instead of sweet smell there shall be stink; and instead of a girdle a rent; and instead of well set hair baldness; and instead of a stomacher a girding of sackcloth; and burning instead of beauty.

In their streets they shall gird themselves with sackcloth: on the tops of their houses, and in their streets, every one shall howl, weeping abundantly.

At the same time spake the LORD by Isaiah the son of Amoz, saying, Go and loose the sackcloth from off thy loins, and put off thy shoe from thy foot. And he did so, walking naked and barefoot.

And in that day did the Lord GOD of hosts call to weeping, and to mourning, and to baldness, and to girding with sackcloth:

Tremble, ye women that are at ease; be troubled, ye careless ones: strip you, and make you bare, and gird sackcloth upon your loins.

And it came to pass, when king Hezekiah heard it, that he rent his clothes, and covered himself with sackcloth, and went into the house of the LORD.

And he sent Eliakim, who was over the household, and Shebna the scribe, and the elders of the priests covered with sackcloth, unto Isaiah the prophet the son of Amoz.

I clothe the heavens with blackness, and I make sackcloth their covering.

Is it such a fast that I have chosen? a day for a man to afflict his soul? is it to bow down his head as a bulrush, and to spread sackcloth and ashes under him? wilt thou call this a fast, and an acceptable day to the LORD?