Cham saw the nakedness of their father, and told his two brothers outside; Shem and Japheth took the garment… and covered the nakedness of their father; their faces were backward, and the shame of their father they did not see. (9:22-23)

Nothing is by chance. Every event in a person's life is predetermined and purposeful. So if a person happens to see something negative in his fellow, he must recognize that he, too, suffers from the same lack in one form or another. Why would Divine providence cause him to see his fellow's degradation if not to open his eyes to his own failing?

One may ask: Perhaps he is being shown his fellow's iniquity not as a message concerning his own personal state, but so that he may assist the other in its correction? Yet, if this were the case, it would not be necessary for him to perceive the guilt and culpability of his fellow, only the fact requiring correction. Were he to be shown his fellow's deficiency for the sole reason that he can do something about it, then this is all he would perceive - the fact of the problem and what he could do to resolve it. If, in addition to this, he also sees and feels his fellow's shame and lowliness, then obviously this aspect of his experience also serves a purpose. Divine Providence has provided him with a mirror with which to discern his own problems.

This is what the verse is telling us with the words "and the shame of their father they did not see": Not only did Shem and Japheth not physically see their father's degradation - this we already know from the (twice-repeated) fact that they turned "their faces backward" - they did not perceive his guilt or disgrace. Unlike Cham, whose own debasement was reflected in his vision of his father's sin, their entire reaction to their knowledge of what had transpired lay in what they must now do to correct it. The shame of their father, however, they simply did not see.

Rabbi Menachem M. Schneerson, the Lubavitcher Rebbe

For many years, Rabbi Israel Baal Shem Tov, who was later to found the chassidic movement, lived a 'hidden' life, artfully concealing his knowledge and piety in the guise of a coarse and ignorant clay digger.

Once, he came to see the rabbi of Brody. The rabbi, seeing only his visitor's crude manners and torn and muddy clothes, treated him with contempt. Said the Baal Shem Tov:

"Our sages tell us to 'learn from every man', for your fellow is your mirror. If your own face is clean, the image you encounter will also be flawless. Should you gaze into a mirror and see a blemish, it is your own imperfection that you are seeing.

"Rabbi of Brody! When I see your sour face, I truly sense how much I myself am lacking in the ideal "love your fellow as yourself."