Isaiah 20:1

That it may be more fully clear that prophets look not to themselves or what lies at their feet but to heavenly things, Stephen, when he was being stoned, saw the heavens open and Jesus standing at the right hand of God. Then he did not feel the blows of the stones, he did not heed the wounds of his body, but, fastening his eyes on Christ, he clung to him. So, too, Isaiah did not notice his nakedness but made himself the instrument of God's voice, that he might proclaim what God spoke within him.

Truly I grieve that while falsehood is so respected, there should be such negligence as regards the truth, that many are ashamed of seeming too devoted to our holy religion, not considering his words who says, "Whosoever shall be ashamed of me before men, of him will I also be ashamed before my Father which is in heaven." But Moses was not thus ashamed, for though invited into the royal palace he "esteemed the reproach of Christ greater riches than the treasures of Egypt." David was not thus ashamed when he danced before the ark of the testimony in the sight of all the people. Isaiah was not thus ashamed when he walked naked and barefoot through the people, proclaiming the heavenly oracles.…But the things that viewed corporeally are unseemly, when viewed in regard to holy religion become venerable, so that they who blame such things will involve their own souls in the net of blame. Thus Michal reproves David for his dancing and says to him, "How glorious was the king of Israel today, who uncovered himself today in the eyes of his handmaids!" And David answered her, "It was before the Lord, who chose me before your father and before all his house to appoint me ruler over the people of the Lord, over Israel."

(Chapter 20, Verse 1) In the year that Tharhaka came to Ashdod, when Sargon the king of Assyria sent him and fought against Ashdod and took it. At that time the Lord spoke by Isaiah the son of Amoz, saying, Go and loose the sackcloth from your waist and take off your sandals from your feet. And he did so, walking naked and barefoot. Then the Lord said, As my servant Isaiah has walked naked and barefoot for three years as a sign and a portent against Egypt and Cush. Thus the king of Assyria will threaten the captivity of Egypt, and the exile of Ethiopia, the young and old stripped and barefoot, with naked buttocks, the disgrace of Egypt. And they will be afraid and ashamed because of their hope in Ethiopia, and because of their glory in Egypt. And the inhabitants of this island will say on that day: Behold, this was our hope, to whom we fled for help, that he might deliver us from the face of the king of Assyria, and how will we be able to escape? We have set the whole content of this chapter, so that we may discuss each part separately. Azotus, which is called Ashdod in Hebrew, was a very powerful city in Palestine among the five cities. It was captured and held by Sargon, the king of the Assyrians, who is also known by seven names, by sending his general named Tartan. At the time when the neighboring city was captured, Isaiah is commanded to walk naked and barefoot, after taking off his sackcloth garment (for this was the prophetic attire of a people grieving for their sins) and his sandals, which the Greek translation calls caligas, thus symbolizing the captivity of Egypt and Ethiopia, who were allies of the Egyptians. In this way, just as Isaiah walked naked and showed his bare buttocks as a sign of disgrace to those who saw, all of Egypt and Ethiopia would become naked and bare, with nothing remaining on the land, as the Assyrians ravaged the region. […]

(Verse 24.) And I fell upon my face, and the spirit entered into me, and set me upon my feet: and he spoke to me, and said to me: Go in, and shut thyself up in the midst of thy house. Unable to bear the weight of the glory of the Lord standing, he fell on his face, so that he could be lifted up by the entering spirit. The spirit stood him upon his feet, and spoke to him, saying: Enter and shut thyself up in the midst of thy house. And this is the meaning: Because you have been strengthened by the vision of the Lord's majesty, you should not fear anyone or be afraid of anything; but rather return to your home or tend to the needs of the body, as some think, or as a sign of the future siege. And just as Isaiah, barefoot and naked (Isaiah 20), proclaimed the captivity of three years and the nakedness of the people, so you, confined to your home, by the action itself, foretell the imminent siege of the city of Jerusalem.

Isaiah goes naked without blushing as a type of captivity to come.