'Sackcloth' in the Bible

Thou hast turned my mourning to dancing for me, Thou hast loosed my sackcloth, And girdest me with joy.

And I -- in their sickness my clothing is sackcloth, I have humbled with fastings my soul, And my prayer unto my bosom returneth.

And I make my clothing sackcloth, And I am to them for a simile.