The Torah tells towards the beginning of Parashat Toledot that Yitzchak loved his older son, Esav, "ki tzayid be-fiv" (literally, "for there was game in his mouth" – 25:28). According to most commentators, the phrase "his mouth" refers to the mouth of Yitzchak. Thus, for example, Targum Onkelos, Ibn Ezra and others explain that Yitzchak developed a particular affinity for Esav because Esav would bring him meat from the hunt. According to Rashi, the term tzayid refers not to actual hunting, but rather to deception. In his view, Yitzchak preferred Esav only because Esav deceptively presented himself as a righteous man, disguising his iniquity under a mask of piety and meticulous halakhic observance.
Rav Shimshon Refael Hirsch, in his commentary, translates this phrase as, "for he was also a hunter with his mouth." According to Rav Hirsch, "his mouth" refers to Esav's mouth, rather than Yitzchak's, and the Torah tells that Yitzchak admired Esav for his hunting skills. Rav Hirsch explains this admiration based on the notion of "the attraction of opposites." He writes:
We see Isaac, risen up again from death on the altar, preferring to withdraw from the bustle of the world and to live quietly in the proximity of the desert…away from the busy traffic of men. That Esau's lusty active nature appealed to him, and that he perhaps saw in him a force which he has lost and could be a support to the home, would be quite possible.
According to Rav Hirsch, Yitzchak preferred Esav because he saw within him what he himself lacked – an "active nature," street-smarts, worldly skills. These talents would serve as a "support to the home" and compensate for the absence of these qualities within Yitzchak's nature.
More recently, Rav Yehuda Henkin, in his work New Interpretations on the Parsha, advanced a similar interpretation, though from a different angle. He, too, explained the term tzayid be-fiv as a reference to Esav's hunting skills, his ability to put "game in his mouth." According to Rav Henkin, Yitzchak admired Esav's self-reliance, his ability to fend for himself and take independent initiative. Yaakov was perceived by his father as lacking this quality of practical know-how and proactive initiative. In choosing the son that would perpetuate the legacy of Avraham, Yitzchak had to decide – so he thought – between Esav, the skilled hunter, and Yaakov, a man of spiritual greatness but who lacked his brother's worldly talents. Rav Henkin describes Yitzchak's choice as follows:
He chose Esau because Esau would be able to father a great people, as Avraham had been promised. The spirituality Esau lacked, he or his children could acquire later. But what good were Yaakov's spiritual qualities, if he was incapable of meeting the challenges of life?
Later, however, when Yaakov deceptively seized the blessings intended from Esav, he demonstrated that he, too, was capable of the same kind of bold initiative as his brother. Therefore, upon discovering that he had blessed Yaakov, rather than Esav, Yitzchak confirmed the blessing ("gam barukh yiheyeh" – 27:33), as he now realized that Yaakov in truth possessed both qualities required of God's special nation: spiritual greatness, and practical know-how; both the "voice of Yaakov," as well as the so-called "hands of Esav."