The Book of Occultation — al-Ṭūsī · Hadith 385 (#Ḥadīth #34)

فأما من زعم أن الأمر قد اشتبه عليه فلا يدري هل لأبي محمد عليه السلام ولد أم لا، إلا أنهم متمسكون بالأول حتى يصح لهم الآخر،فقوله باطل بما دللنا عليه من صحة إمامة ابن الحسن وبما بينا من أن الأئمة اثنا عشر. ومع ذلك لا ينبغي التوقف بل يجب القطع على إمامة ولده،وبما قدمناه أيضا من أنه لا يمضي إمام حتى يولد له ويرى عقبه. ويؤكد ذلك ما رواه:

As for the one who thinks that the situation is confusing to him and he does not know whether Imam Hasan Askari did have a son or not, and that he will adhere to the Imamate of Imam Hasan Askari until it is proved that he had a son, his assertion is invalid, because we proved the Imamate of Ibn Hasan and we proved that the Imams are twelve. Retaining these proofs in mind, one need not be confused, but rather, it is most convincing that Hasan’s son is the Imam. It is further strengthened by our proofs that no Imam passes away until he sires an heir and sees his legatee.

Gradings are classical jarḥ-wa-taʿdīl, name-matched to a rijāl index (not individually re-verified).