'Sackcloth' in the Bible

A putrid stench will replace the smell of spices, a rope will replace a belt, baldness will replace braided locks of hair, a sackcloth garment will replace a fine robe, and a prisoner's brand will replace beauty.

In their streets they wear sackcloth; on their roofs and in their town squares all of them wail, they fall down weeping.

At that time the Lord announced through Isaiah son of Amoz: "Go, remove the sackcloth from your waist and take your sandals off your feet." He did as instructed and walked around in undergarments and barefoot.

At that time the sovereign master, the Lord who commands armies, called for weeping and mourning, for shaved heads and sackcloth.

Tremble, you complacent ones! Shake with fear, you carefree ones! Strip off your clothes and expose yourselves -- put sackcloth on your waist!

When King Hezekiah heard this, he tore his clothes, put on sackcloth, and went to the Lord's temple.

Eliakim the palace supervisor, Shebna the scribe, and the leading priests, clothed in sackcloth, sent this message to the prophet Isaiah son of Amoz:

I can clothe the sky in darkness; I can cover it with sackcloth."

Is this really the kind of fasting I want? Do I want a day when people merely humble themselves, bowing their heads like a reed and stretching out on sackcloth and ashes? Is this really what you call a fast, a day that is pleasing to the Lord?