What was Ham's sin?

Please give Catholic teaching regarding “Nakedness of his father”. In scripture

Genesis 9:20-24

Noah, a man of the soil, was the first to plant a vineyard. He drank some of the wine, became drunk, and lay naked inside his tent. Ham, the father of Canaan, saw his father’s nakedness, and he told his two brothers outside. Shem and Japheth, however, took a robe, and holding it on their shoulders, they walked backward and covered their father’s nakedness; since their faces were turned the other way, they did not see their father’s nakedness. When Noah woke up from his wine and learned what his youngest son had done to him…

There is no one singular Catholic explanation of this passage. Throughout history there have been various explanation given by commentators:[list]
*] Ham’s action of “saw his father’s nakedness” might be an expression for some kind of assault that Ham perpetrated upon the passed out Noah. This seems a reasonable reading yet it would seem unreasonably odd for Ham to then brag about it to his brothers.
*] The expression “saw his father’s nakedness” might mean to have relations with his father’s wife. The idea is that Ham did this as a kind of “power play” to assert himself as the dominant male in the new world which would then explain why he told everyone else. But if the “nakedness” refers to Noah’s wife then it seems strange that while the brothers covered her up, Ham is not described as uncovering her.
*] The passage can also be taken literally. This would mean that nothing more happened than Noah passed out drunk and naked and that rather than treat his father with respect Ham instead scoffed at his condition and then gossiped about it to others.
Personally I prefer the literal interpretation. Gossip was considered a major sin in an Judaism, see Judaism 101’s Speech and Lashon Ha-Ra

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