Genesis 9:22-24

Ham, the father of Canaan, saw the nakedness of his father, and told his two brothers outside. But Shem and Japheth took a garment and laid it upon both their shoulders and walked backward and covered the nakedness of their father; and their faces were turned away, so that they did not see their father’s nakedness. When Noah awoke from his wine, he knew what his youngest son had done to him.