Jonah 3:5, 8

The people of Nineveh believed and trusted in God; and they proclaimed a fast and put on sackcloth [in penitent mourning], from the greatest even to the least of them.

But both man and animal must be covered with sackcloth; and every one is to call on God earnestly and forcefully that each may turn from his wicked way and from the violence that is in his hands.