Genesis 9:23

And Shem and Japheth took a garment, and laid it upon both their shoulders, and went backward, and covered the nakedness of their father; and their faces were backward, and they saw not their father's nakedness. Even though Noah had sinned, it was not the business of the sons to make mockery of the fact. Shem and Japheth did what filial reverence demanded of them when they covered the shame of their father without so much as looking at him. Thus they also showed the chasteness of their mind. This behavior may well serve as a lesson for our day and age, when sexual matters are always kept in the foreground, either by prurient speech and behavior or by shameless exposure of nakedness.