Genesis 9:21-25

He drank of the wine and became drunk, and he uncovered himself within his tent. Ham, the father of Canaan, saw his father’s nakedness and told his brothers outside. But Shem and Japheth took a cloth, placed against both their backs, and, walking backward, they covered their father’s nakedness; their faces were turned the other way, so that they did not see their father’s nakedness. When Noah awoke from his wine and learned what his youngest son had done to him, he said: “Cursed be Canaan; the lowest of slaves shall he be to his brothers.” [Translation by Rabbi Steven Greenberg]