《后汉书·列传·荀韩钟陈列传》
在众多的礼仪中，婚姻的礼仪第一。所以天子娶十二，是天数如此，诸侯以下各有等差。事物的品级如此。
诸侯以下各有等差，事之降也。
Among the many rituals, marriage ritual was first. Therefore, the Emperor had twelve concubines; this was the rule of heaven, and feudal lords and princes had their respective ranks. The categories of things were thus established.