One can only begin to imagine what must have gone through Yaakov’s mind as he approached his father to accept his blessing. Yaakov, the man noted for his integrity, was acting in a seemingly deceptive manner. His mother had instructed him to act this way as the last resort, the only way to obtain his rightful blessings. He had acquired the birthright “fair and square;” he was only collecting his due. Nonetheless, dressing up as Eisav, even if it was at the behest of his mother, was still not typical of Yaakov.
Yaakov dressed up with “hairy” clothes to give himself the appearance of Eisav. Yitzchak, however, still was not sure. He asked Yaakov to approach him, but that was not sufficient. On the contrary, there seemed to be an inconsistency between Yaakov’s “Eisav-like” hairy hands and his voice, which gave a “Yaakov-like” impression. Yitzchak discerned a difference in their voices although, according to Chazal, their voices sounded the same. It was the manner in which he expressed himself that differentiated Yaakov from Eisav.
Two characteristics distinguished Yaakov’s voice from that of Eisav: He always invoked the Name of Heaven and he spoke gently. Eisav, the worldly man who believed in his own might, attributed his triumphs and successes to himself; his strength, his mind, his cunning, Yaakov recognized and acknowledged the true Source of all success – and failure. Consequently, he immediately attributed his swift “return” to Hashem.
Yaakov’s expression caused him serious concern. In fact, the Midrash compares him to a raven who carries a burning hot coal – successfully moving from place to place, but burning its wings in the process. Why did Yaakov endanger himself? He could as easily have “talked” like Eisav, just as he dressed like him. Why did he commit this fatal error?
The Imrei Emes explains that while Yaakov was actually aware of his endangerment, he could not even for a single moment abrogate Hashem’s “part” in everything that he had accomplished. There are some areas of human endeavor that become so natural, so ingrained in one’s psyche, that it is impossible to divorce oneself from them. For Yaakov, the Hashem “component”, recognizing that everything is from the Almighty, was a natural element in his personality.
This is an area in which Yaakov and Eisav were different. Horav Bunim z.l., m’Peshischa comments that one should not make the mistake of assuming that Eisav looked like a criminal, uncouth and villainous. No! Eisav dressed like a Rebbe; he even said divrei Torah during Seudah Shlishis! For all outward appearances, Eisav gave the impression of being a saint. Indeed, he would ask profound questions concerning Halachah. He could put on a show in every respect, except one: he could not mention Hashem’s Name. He could not attribute his success to the true Source. He just could not say, “Baruch Hashem.” This was Yaakov’s distinctiveness: he could put on Eisav’s hunting clothes; he could attempt to outwardly act like him; but he could not speak like him.
The second area that impressed Yitzchak was the gentle manner in which his son spoke to him. This could not be Eisav. This had to be Yaakov. The Maharal says that when Yaakov mentioned Hashem’s Name, Yitzchak began to question the identity of the speaker who stood before him. When Yaakov spoke in his gentle, respectful tone, he knew for sure that Eisav was not standing before him. Horav Moshe Reis, Shlita, derives from here that mentioning Hashem’s Name, attributing success to the Almighty, is still not proof-positive of one’s true affiliation. One can conceal his real personality and talk like a man of virtue and conviction. One cannot, however, fabricate gentility and refinement. That is part of a person’s innate character. When Yitzchak heard the respectful manner in which he was addressed, he knew that it could not be Eisav standing before him.