ותכהין עיניו מראות. משום שאהב עשו כי ציד בפיו וכתיב כי השחד יעור. ד"א כדי שיבא יעקב ויטול את הברכות ולהא דפרש"י שכהו עיניו מעשן ע"ז קשה קצת למה לא כהו ג"כ עיני רבקה. ואומר המדרש משל למקיש כלי עצם בכלי חרש הכלי חרש משתבר אבל מקיש כלי עצם לכלי עצם אין משתבר זה מזה כך יצחק נברא מן האדמה לכך הזיקו לו מעשה כלותיו שנבראו מן הצלע אבל רבקה שנבראת מן העצם כמו כן לא הזיקו לה מעשה כלותיה: ותכהינן עיניו מראות, “his eyes had become weak from seeing (too much).” One opinion cites Exodus 23,8 where the Torah tells us that accepting a bribe corrupts, i.e. blinds the eyes of even normally honest judges. Yitzchok accepting venison hunted by his son Esau, caused him to overlook the numerous shortcomings of his son Esau without rebuking him. An alternate explanation of the word: מראות, “from seeing.” G–d weakened his eyesight in order to enable Yaakov to secure Esau’s blessing for himself. This is presumably the reason why Rashi wrote that his eyesight became impaired from the smoke rising from the animals offered as sacrifices to a variety of idols. (Tanchuma, 8) The Midrash there explains this by means of a parable. When a person has two implements at his disposal, one made of bone, the other of earthenware. When he chooses to perform certain tasks with the earthenware implement for which it was not designed, it is liable to break into pieces. On the other hand, if he were to perform the same task with the implement made out of horn, it would not break into pieces. Yitzchok who was Avraham’s son, i.e. made of earth as G–d had made Adam, could not tolerate the smoke from these offerings of his daughters-in-law. Rivkah, being a woman, i.e. her origin was the bone of the first woman from which Chavah had been constructed, was not affected by that smoke.
ויקרא אל עשו בנו הגדול. מכאן שמחניפין לרשעים בשעתן. דבר אחר לפי שהעולם בידו קראו גדול: ויקרא את עשו בנו הגדול, “he called his senior son Esau.” From this adjective used by Yitzchok when calling Esau, we learn that when fortune smiles on the wicked it is permitted to flatter them. An alternate explanation for the word הגדול: seeing that Esau was such an important person at that time, replacing Nimrod, he is described as “the great.”