Adam Clarke on Genesis 27:23

And he discerned him not, because his hands were hairy - From this circumstance we may learn that Isaac's sense of feeling was much impaired by his present malady. When he could not discern the skin of a kid from the flesh of his son, we see that he was, through his infirmity, in a fit state to be imposed on by the deceit of his wife, and the cunning of his younger son.