Charles Ellicott Commentary Genesis 9:22-23

"And Ham, the father of Canaan, saw the nakedness of his father, and told his two brethren without. 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." — Genesis 9:22-23 (ASV)

Ham ... saw ... and told. —The sin was not in seeing, which might be unintentional, but in telling, especially if his purpose was to ridicule his father. His brothers, with filial piety, take a garment, the loose outer robe or cloak enveloping the whole body, and with reverent delicacy walk backwards, and lay it upon their father’s person.