‘And Shem and Japheth took a robe (shimlah - which acted as a blanket at night and a robe during the day - see Exodus 22:26) and laid it over their shoulders, and went in backwards and covered their father's nakedness, and their faces were backwards and they did not look on their father's nakedness.'
In contrast to Ham, Shem and Japheth act with consideration towards their drunken father and preserve his dignity, thus also avoiding any unpleasant thoughts that might arise. This is a good example of the importance of taking steps to avoid temptation.