“They did not see their father’s nakedness” (9:23)
When a person sees another stumble in an inappropriate act, there are two possible reactions: a) one is disgusted by the act, or b)one thinks what can be done to help the person.
Cham took the former approach, “he looked at his father’s nakedness” (v. 22) i.e. he focused on the inappropriateness of the situation. Sheim and Yafes, on the other hand, “did not see their father’s nakedness,” i.e. they did not become disgusted at what had occurred. They simply took action to correct the situation.
What leads people to react in these two different ways? The Ba’al Shem Tov taught that a person who is himself unclean sees and is frustrated by the uncleanliness of others. A pure person sees only that his fellow is in need of help.
(Based on Likutei Sichos vol. 10, p. 24ff.)