'Sackcloth and Ashes' in the Bible

When Mordecai perceived all that was done, he rent his clothes, and put on sackcloth and ashes, and went out into the midst of the city, and cried loud and lamentably,

Should it be such a manner of fast that I should chose? A day that a man should hurt his soul in? Or to bow down his head like a bulrush? Or to spread sackcloth and ashes under him? Shouldest thou call this a fast, and a day acceptable unto the LORD?