'Sackcloth' in the Bible

And his servants say unto him, 'Lo, we pray thee, we have heard that the kings of the house of Israel -- that they are kind kings; let us put, we pray thee, sackcloth on our loins, and ropes on our heads, and we go out unto the king of Israel; it may be he doth keep thee alive.'

And they gird sackcloth on their loins, and ropes are on their heads, and they come in unto the king of Israel, and say, 'Thy servant Ben-Hadad hath said, Let me live, I pray thee;' and he saith, 'Is he yet alive? he is my brother.'

And it cometh to pass, at Ahab's hearing these words, that he rendeth his garments, and putteth sackcloth on his flesh, and fasteth, and lieth in sackcloth, and goeth gently.