Kommentar zu Bereschit 9:22

וירא חם אבי כנען AND HAM THE FATHER OF CANAAN SAW — Some of our Rabbis say that Canaan saw it and told his father about it, and on that account he is mentioned in connection with this matter and was cursed (Genesis Rabbah 36:7).

וירא חם אבי כנען את ערות אביו, he saw the shameful deed his son כנען had done to his father Noach when he had castrated him. (according to some of our sages in Sanhedrin 70) According to the historian Berussi Hacaldaii, (compare Genesis 6,9) Canaan castrated his grandfather not surgically, but by some means of sorcery. His father Cham watched his son invoke the witchcraft without protesting or trying to stop him. Disgrace, shame, is also called ערוה, “nakedness.” Compare Ezra 4,14 וערות מלכא לא אריך לנא למחזא “it is not right that we should see the king being disgraced.” Also, in Deuteronomy 21,4 the expression ערות דבר does not refer to either literal nakedness, or to sexual licentiousness, or incest, but refers to “a disgraceful thing.”

וירא, by feasting his eyes on his father’s nudity, Cham showed that he was the father of Canaan, i.e. that his son already had inherited a genetic flaw. The additional impropriety he committed was that he told his brothers about it, instead of first covering his father’s nudity.