Kommentar zu Bereschit 27:22

THE VOICE OF JACOB, because he speaks in an entreating strain —“Arise I pray thee.” Esau, however, spoke in a harsh strain (v. 31) “Let my father arise” (Midrash Tanchuma, Toldot 11).

הקול קול יעקב, seeing that Esau and Yaakov were twins, their voices were similar to one another. This made it easy for Yitzchok to err as to who was in front of him if he were to rely only on his sense of hearing. Having first established that unlike Yaakov who was smooth skinned, the son in front of him was hairy, Yitzchok was now faced with a dilemma whether to trust his sense of hearing or his sense of touch.

והידים ידי עשו. There can be no question that the skins had been prepared in such a fashion that the hair on them were just like the hair on human skin, for in its natural state the hair on goatskin is considerably different from that on a human skin. What the Torah testifies to then is that Yaakov’s hands now were just as hairy as the hands of Esau. It is quite possible that not only Yitzchok’s eyesight had deteriorated to the point where it did not serve him to identify objects with any degree of certainty, but that also his sense of touch had become weakened as a source of identifying objects he touched. Samuel II 19,36-37 would support this where Barzilai lists a number of his faculties which suffered weakness as a result of old age.