《论衡·卷六·祸虚篇》
子夏失明，是由于丧子。对子女疼爱，是人共同的感情；对父母恩情，是人应竭力报答的。
然子夏之丧明，丧其子也。子者人情所通，亲者人所力报也。
Zixi's blindness is due to the loss of his son. Love for children is a common human emotion, and the kindness of parents should be repaid by humans.