《北齐书·列传·卷四十四》
所以《礼记丧服》说： 妾所生的儿子三年之内不做长子，不能继承祖先的基业并祭祀祖先。 《礼记》记载了公仪仲子死时的情景： 擅弓说： 这是怎么回事呢，我以前没有听说过，仲子没有立嫡孙反而立庶子为继承人，这是什么原因呢? 
故丧服曰： 庶子不为长子三年，不继祖与祢也。 礼记公仪仲子之丧： 檀弓曰：子服伯子曰： 郑注曰： 伯子为亲者讳耳，立子非也。
Therefore, the "Book of Rites, Mourning Clothes" says: The son born to a concubine does not become an eldest son within three years, and cannot inherit the ancestral property and worship the ancestors. The "Book of Rites" records the scene when Gongyi Zhongzi died: Shan Gong said: What's going on? I never heard of this before. Zhongzi did not establish an嫡孙 but instead established a庶子 as his heir. What's the reason?