Charles Ellicott Commentary Genesis 27:21

"And Isaac said unto Jacob, Come near, I pray thee, that I may feel thee, my son, whether thou be my very son Esau or not." — Genesis 27:21 (ASV)

Come near ... that I may feel thee.—Besides the answer, given in a style very different from Esau’s way of thinking, Isaac was surprised by the short delay in bringing the savoury meat; for the game had to be sought at a distance from the cattle pastures.

Although the voices of the twins also had a certain degree of similarity, they nevertheless possessed their own peculiarities, and Isaac detected the difference.

But the artifice of the kid-skins, fitted (no doubt) cleverly to Jacob’s hands and neck, saved him from detection; for after Isaac had passed his hands over him, his doubt entirely vanished.