TT #61 · Parashas Noach · Fifth Aliyah · Passuk 9:24
Noach awoke from his wine and knew what his youngest son had done to him.
Torah Temimah points to the dispute of Rav and Shmuel (Sanhedrin 70a) — castration vs. sexual violation.
E-Daf image — Sanhedrin 70a (size=3)
English: “What he had done to him” — Rav and Shmuel: one said he castrated him, and one said he sexually violated him. According to the one who said he castrated him: because he prevented a fourth generation, the curse fell on the fourth (Canaan).
Custom (two opinions on the nature of Cham’s act).
Cham’s offense was either castration or sexual violation; the curse on Canaan is measure-for-measure with the former view.