27:1כ״ז:א׳
1 א

ותכהין. בַּעֲשָׁנָן שֶׁל אֵלּוּ. דָּ"אַ כְּשֶׁנֶּעֱקַד עַ"גַּ הַמִּזְבֵּחַ וְהָיָה אָבִיו רוֹצֶה לְשָׁחֳטוֹ, בְּאוֹתָהּ שָׁעָה נִפְתְּחוּ הַשָּׁמַיִם וְרָאוּ מַלְאֲכֵי הַשָּׁרֵת וְהָיוּ בוֹכִים, וְיָרְדוּ דִמְעוֹתֵיהֶם וְנָפְלוּ עַל עֵינָיו, לְפִיכָךְ כָּהוּ עֵינָיו. דָּ"אַ כְּדֵי שֶׁיִּטֹּל יַעֲקֹב אֶת הַבְּרָכוֹת:

ותכהין HIS EYES WERE DIM through the smoke raised by these women in offering incense to idols (Midrash Tanchuma, Toldot 8). Another explanation is: When Isaac was bound upon the altar and his father was about to slay him, at that very moment the heavens opened, the ministering angels saw it and wept, and their tears flowed and fell upon Isaac’s eyes which thus became dim (Genesis Rabbah 65:5). Another explanation is: They became dim just in order that Jacob might receive the blessings (Genesis Rabbah 65:8).