Thanks for your question.
According to Genesis 9:20-25, Noah raised grapes after the flood, one day he sampled too much of his wine and became drunk. While he was drunk, he lay naked in his tent. Ham saw his father naked, and told his brothers Shem and Japheth about it. Shem and Japheth went into the tent with their faces away from him, and covered him. When Noah awoke, he realized what had had been done to him, and cursed Canaan, son of Ham, to be the servants of Shem and Japheth.
What did Ham do? Did he:
1. Merely see his father naked in the tent and then laughed about it to the rest of the family? This can hardly be the case. In those days, they might well have seen each other virtually naked quite frequently.
2. Was it something more severe than that? Was Ham guilty of a sodomistic rape of his father? It appears that the crime was more than just one of immodesty and disrespect. I Gen 9:24 we read that when Noah awoke, "he knew what his younger son had done unto him" So, Ham had "done" something to Noah and it was in connection with his nakedness. That leaves little room for doubt. Also compare Genesis 34:2 "And when Shechem the son of Hamor the Hivite, prince of the country, saw her, he took her, and lay with her, and defiled her." Dinah was probably naked at the time, possibly bathing at the home of one of her Shechemite friends - like David's sin with Bathsheba. In the same way, Ham could have defiled his father.
3. Leviticus 18 is quite specific about one who does such a thing. Lev. 18:24 "For whosoever shall commit any of these abominations, even the souls that commit them shall be cut off from among their people."
4. The Jewish commentary, the Talmud, goes further than this. It suggests that because Noah had 3 sons and he cursed Ham in the name of Ham's 4th son, Canaan, that Ham had physically damaged Noah so that he coudn't himself have a 4th son or perhaps Ham (like Reuben with Jacob's wife and Absalom with David's wives) went in to his mother and raped her because Noah was incapacitated and couldn't protect her. After that, Noah might not have been able to have a sexual relationship with her - notions of "defilement" being what they were back then. Perhaps, like Reuben and Absalom, by having sex with his own mother, he thought to assert his authority in the family. Perhaps that's why he informed his brothers - "I'm now head of the family." He would have had to have been a bit crazy to have done this but the other options don't indicate a sound mind either! Thus, instead of being the leader of his brethren, he became their servant.
Whatever Ham actually did, it was horrible enough to deserve the strongest denunciation.
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I hope you have found this helpful.