The Book of Occultation — al-Ṭūsī · Hadith 395 (#Ḥadīth #44)

فلا تكون بعد علي بن الحسين عليه السلام إلا في الأعقاب وأعقاب الأعقاب.

Thus after Ali Ibn Husain Imamate continued in his generations one after another.

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