大般涅槃經義記 6.314

6.314

如來許為作定心中，佛先告眾「世王有疑，我為作定」。是義云何？世王向者道聞二言便生疑念，不知如來肯見救濟令如須那？為當不救令如流離、瞿迦離等墮阿鼻獄？准下見佛，除疑決定，疑意正爾。佛下領命，令其知佛定欲救濟名作定心。

In the Tathāgata's promising to make his mind resolute, the Buddha first addresses the assembly: "King Ajātaśatru has doubts; I shall make his mind resolute." What does this mean? King Ajātaśatru just now heard the two statements on the road and immediately gave rise to doubts, not knowing whether the Tathāgata would be willing to rescue him and make him like Sunakkhatta, or whether he would not rescue him and let him be like Virūḍhaka, Kokālika, and the others, falling into the Avīci hell. Judging from his subsequent meeting with the Buddha, where his doubts are removed and he attains certainty, his doubtful intention was precisely this. The Buddha below accepts the task and causes him to know that the Buddha definitely intends to rescue him, which is called "making his mind resolute."