Midrash su Isaia 20:4

R. Simeon the son of Lakish maintained: Shem’s descendants also became slaves, as it is said: And if thy brother, a Hebrew man or a Hebrew woman, be sold unto thee (Deut. 15:12). Shem’s descendants, however, are freed at the expiration of six years, of servitude, as it is written: Then in the seventh year thou shalt let him go free (ibid.), while the descendants of Ham are never freed, as is said: You may hold them to service forever (Lev. 25:46). Therefore, he remains a lifelong slave and does not go forth into the world a free man. Why was this curse imposed upon him? Because he was responsible for his father’s degradation. Thus, the Holy One, blessed be He, brought retribution upon the descendants of Ham by humiliating them by means of the king of Asshur, as it is said: So shall the king of Assyria lead away the captives of Egypt and the exiles of Ethiopia, young and old, naked and barefoot (Isa. 20:4).

(Gen. 9:25:) AND HE SAID: CURSED BE CANAAN. Ham looked; is Canaan cursed?⁸³Gen. R. 36:7. R. Judah said: The curse does not coexist with a blessing. < Ham could not be cursed > because it is stated (in Gen. 9:1): THEN GOD BLESSED [NOAH AND HIS CHILDREN. R. Nehemiah said:] Canaan had looked and told his father; so the curse had returned to its source. For that reason it is stated (in Gen. 9:25): CURSED BE CANAAN. Our masters have said: When Noah was in the ark, he said: Oh, that my children had slaves so that, while they were seated, those < slaves > would go forth before them. When, however, I go out from the ark, whomever I beget I shall make into slaves for them. He said to him (Ham): You did not allow me to beget a fourth son who would be a slave for his brothers.⁸⁴See Sanh. 70a, according to which Rav maintained that Ham had castrated his father. By your life, I am making your fourth son a slave. Thus it stated (in Gen. 9:25): AND HE SAID: CURSED BE CANAAN; [A SLAVE OF SLAVES SHALL HE BE TO HIS BROTHERS]. Resh Laqish said: Behold, those from Ham are slaves forever, but the children of Shem go forth into the world free. Thus it is stated (in Deut. 15:12, 17): IF THERE IS SOLD TO YOU < A FELLOW HEBREW, MAN OR WOMAN … IN THE SEVENTH YEAR YOU SHALL SET HIM FREE >…. THEN YOU SHALL TAKE AN AWL < AND PUT IT THROUGH HIS EAR INTO THE DOOR >. What is written there (in vs. 17)? AND HE SHALL BE YOUR SLAVE FOREVER. Here, however, is a slave of slaves, < i.e., > a slave who does not take his freedom and never goes away. What caused this curse for him? < It came about > because he had treated his father with contempt. So also the Holy One is going to exact punishment from the children of Ham and humiliate them at the hands of the king of Assyria, as stated (in Is. 20:4): SO SHALL THE KING OF ASSYRIA DRIVE OFF < THE CAPTIVES OF EGYPT AND THE EXILES OF NUBIA > … [NAKED AND BAREFOOT]. What is the meaning of NAKED AND BAREFOOT? That he would humiliate them and parade them naked. Now, in regard to Japheth, who honored his father, how does the Holy One repay him? When Gog (Japheth's descendant) comes, the Holy One will overshadow him and cover him over, as stated (in Ezek. 39:11): AND IT SHALL COME TO PASS IN THAT DAY THAT I WILL GIVE UNTO GOG A BURIAL PLACE THERE IN ISRAEL. And how did he reward Shem? When the sons of Aaron came in to offer sacrifice, their bodies (according to Lev. 10:2) were burned but their clothes were not burned.⁸⁵Cf. Shab. 113b; Sanh. 52a, according to which their bodies were not burned. Why? Because they were children of Shem. That is how it is with the righteous. But where is it shown about the wicked? When Sennacherib went up to Jerusalem, and all his soldiers with him, their bodies were burned and their clothes were not burned. Why? Because they were children of Shem, as stated (in Gen. 10:22): THE SONS OF SHEM ARE ELAM, ASSHUR, ARPACHSHAD, LUD, AND ARAM.

"And Shem and Yafet took a garment (Gen. 9:23)". R. Yochanan said: Shem began the mitzvah, then Yafet came and listened to him. Therefore Shem was granted a tallit and Yafet a phallium [circumcision]. 'And laid it upon both their shoulders and went backwards and covered their father's nakedness' but since it is written 'went backwards' don't we [already] know that they did not see their father’s nakedness? This comes to teach that they covered their faces with their hands and walked backwards, giving him the respect due from a son to a father. Said the Holy One of Blessing to Shem: ‘You covered your father’s nakedness! By your life [I swear that] I will reward you 'When these men are bound in their cloaks (be-sarbelehon),’ etc. (Dan. 3:21). Rabbi Yudan and Rabbi Huna disagree [on what ‘be-sarbelehon’ means]: Rabbi Yudan said: It means in their prayer cloaks; Rabbi Huna said: It means in their robes of state. The Holy One of Blessing said to Yafet: ‘You covered your father’s nakedness! By your life [I swear that] I will reward you 'for it shall come to pass in that day, that I will give to Gog a place fit for burial in Israel’ (Ezek. 39:11) The Holy One of Blessing said to Ham: ‘You brought your father’s nakedness to disgrace: By your life [I swear that] I will punish you: 'So shall the king of Assyria lead away the captives of Egypt, and the exiles of Ethiopia, young and old, naked and barefoot, and with buttocks uncovered to the shame of Egypt’ (Isa. 22:4).