The words "There are three ways to be unfilial, and the worst is to be without issue," come from the first half of the fourth chapter of Mencius, one of the "Four Books" of the Confucianist canon.
「不孝有三，無後為大」出自孟子離婁章句上篇。全文為「不孝有三，無後為大。舜不告而娶，為無後也。