Genesis 9:24

And Noah awoke from his wine
From his sleep, which his wine brought on him; when the force and strength of that was gone, and when not only he awaked, but came to himself, and was sober;

and knew what his younger son had done to him;
either by revelation, as some, or prophecy, as Ben Gersom, or by the relation of his two sons, whom, when finding himself covered with another's garment, he might question how it came about, and they told him the whole affair: some, as Aben Ezra, Ben Gersom, and Abendana, think that this was not Ham, the younger son of Noah, and whom some also will have not to be the youngest, being always placed middlemost, but Canaan, the fourth and youngest son of Ham; and whom Noah indeed might call his younger, or "his son, the little one" ^F16; as it was usual for grandchildren to be called the sons of their grandfather; see ( Genesis 29:5 ) and Noah might be informed how his little son, or rather grandson Canaan, had been in his tent, and seeing him in the posture he was, went very merrily, and told his father Ham of it, who made a jest of it also; and this seems the more reasonable, since Canaan was immediately cursed by Noah, as in the following verse; (See Gill on Genesis 9:22) this affair must happen many years after Noah's coming out of the ark, since then his sons had no children; whereas Ham had at this time four sons, and Canaan was the youngest of them; and he was grown up to an age sufficient to be concerned in this matter, of treating his grandfather in an ill way, so as to bring his curse upon him: Jarchi interprets "little" by abominable and contemptible, supposing it refers not to age, but character, and which was bad both in Ham and Canaan: (See Gill on Genesis 9:22).