《资治通鉴·宋纪·宋纪一》
皇子拓跋焘，年将十二岁，聪明睿智，性情温和，以长子立为太子，是礼制的最高原则，如果一定要等到他们长大成人，再在他们中间选择太子，那就很可能废长立幼，使天伦倒错，从而召致天下大乱。 
皇子焘年将周星，明睿温和，立子以长，礼之大经，若必待成人然后择之，倒错天伦，则召乱之道也。 
“The prince Tuoba Dao, who is about twelve years old, is smart, wise, and gentle. It is the highest principle of etiquette to establish the eldest son as the crown prince. If we must wait until they grow up and then choose the crown prince from among them, it is very likely that we will abolish the elder and establish the younger, which will lead to a chaotic world.”