“His eyes weakened due to seeing.” (Bereshis 27,1)
According to the plain meaning of the text, a decline in the quality of vision is a normal phenomenon in people who reach a certain age, we find such a phenomenon as occurring to the prophet Achiyah Hashiloni (Kings I 14,4). When the Torah testified that Moses at 120 had not lost any part of his vision or any other bodily functions, (Deut. 34,7) this is reported precisely because it was a miracle.
A Midrashic approach: Bereshit Rabbah 65,7 attributes Yitzchak’s failing eyesight to his being bribed with venison by his son Esau. The Torah had taught in Exodus 23,8 that one must not accept bribes and that accepting bribes “blinds the eyes of the seeing.” At that point, the Torah addresses judges and warns them not to accept bribes. Continuing with that subject, Rabbi Yitzchak said: “if someone who accept bribes from someone (such as his son who is obligated to feed him in his old age) is punished for accepting such favours, how much more is this true of someone who accepts such favours from a person who does not owe him anything!” Another approach of a homiletical nature is this: Yitzchak’s eyesight was impaired in order to enable Yaakov to obtain the blessing (Tanchuma Toldot 8). Still another approach: Yitzchak’s failing eyesight was due to the smoke from the incense his daughters-in-law offered to idols. [This leaves open why Rivkah’s eyes were not similarly affected. Maybe because she was so much younger. Ed.] Yet another reason offered in the Midrash: It was to prevent Yitzchak from leaving his house so that when people saw him they should not point to him as the father of the wicked Esau (compare Bereshit Rabbah 65,10). G’d hit on a stratagem to keep him indoors by blinding him. This would be reflected in the verse (Proverbs 28,28) “when the wicked rise up, other men go into hiding;” this prompted our sages to say that if someone raises a son who turns out to be wicked his eyes will become dimmed. They quote what happened to Yitzchak as proof for their contention. The reason that Achiyah Hashiloni lost his eyesight was that Jerobam ben Nevat, the King who placed golden calves on the road to Jerusalem to prevent his subjects from travelling to the Temple, was his star pupil.
A totally different approach (Bereshit Rabbah 65,10) ascribes Yitzchak’s failing eyesight not to his age but to the fact that while he was bound on the altar he had beheld a forbidden vision of G’d, something which G’d did not want to punish him for at that stage. However, G’d decreed at that very hour that He would deprive Yitzchak of his eyesight at some time in the future. If G’d had punished Yitzchak immediately, He would have subjected not only Avraham to a test but also Yitzchak; this was not His intention at the time. This is based on the Torah writing מראות, “as a result of seeing something.” Had the Torah simply wanted to inform us that Yitzchak’s failing eyesight was a normal phenomenon it would have written מלראות, i.e. “his eyes became too weak to see.” Bereshit Rabbah 65,10 illustrates this with a parable. A King went for a private stroll behind the gate of his palace. When he raised his eyes, he noticed that the son of a dearly beloved friend espied him from his window. Thereupon the King reasoned as follows: “if I kill that son, I will cause anguish to my friend. I will instead decree that the windows all be closed so that the son in question can no longer use it to spy on me.” A similar thing happened during the binding of Yitzchak. If G’d had punished Yitzchak for not closing his eyes and watching something he was not supposed to watch, He would be causing anguish to Avraham at the very moment when He was testing him. This is the meaning of Isaiah 5,23 וצדקת צדיקים יסירו ממנו מצדיקי רשע עקב שוחד, “who vindicate him who is in the wrong in return for a bribe, and withhold vindication from him who is in the right.” The prophet alludes to Yitzchak who, because of the venison he used to provide for his father, enjoyed his father’s favour. The second half of the verse refers to Moses and the fact that his eyesight was not withheld from him even at the age of 120 as he had never accepted any bribe.
