《左传·昭公·昭公三十二年》
所以天有三辰，地有五行，身体有左右，各有配偶，王有公，诸侯有卿，都是有辅助的。
故天有三辰，地有五行，体有左右，各有妃耦。王有公，诸侯有卿，皆有贰也。
Thus, there are three celestial bodies in heaven, and five elements on earth, and people have left and right arms, all having companions. A king has a duke as his assistant, and feudal lords have ministers as their assistants.