《资治通鉴·唐纪·唐纪三十》
古代制定礼仪的人知道人们容易感情用事，恐怕逐渐违背了礼仪，所以规定不同的亲属关系服丧不同，其中有很大的差别，就是让后代人永远不要把它们相混。
古之制作者，知人情之易摇，恐失礼之将渐，别其同异，轻重相悬，欲使后来之人永不相杂。
The ancients who formulated the etiquette knew that people were easily influenced by emotions, and were afraid that the etiquette would gradually be violated, so they规定 that different relatives would serve mourning clothes differently, with great differences, so that future generations would never confuse them.