In Parshat Toldot, we learn that Yitzchak became blind in his old age. Rashi cites three explanations from the Midrash and Talmud as to why this happened. One explanation is that Esav’s wives burned incense to idols, and the smoke from that idolatry caused Yitzchak’s blindness. This great tzaddik could not tolerate such tumah—such impurity. […]