Isaiah 20:2

at the same time spake the Lord by Isaiah, the son of Amoz, in the year when the siege of Ashdod began, saying, Go and loose the sackcloth, the loose outer garment of coarse cloth which Isaiah wore, from off thy loins and put off thy shoe from thy foot. And he did so, walking naked, that is, with only his tunic or shirtlike garment, and barefoot, presenting the appearance of one who bad been robbed or spoiled, stripped of his possessions, like a beggar or captive of war. The very dress of Isaiah called attention to his message of repentance.