The Book of Occultation — al-Ṭūsī · Hadith 675 (#Ḥadīth #1)
Chapter 50 | Time of reappearance of the Imam
وأما وقت خروجه عليه السلام فليس بمعلوم لنا على وجه التفصيل، بل هو مغيب عنا إلى أن يأذن الله بالفرج.
We are not aware of the exact time of the reappearance of the Imam ; on the contrary he is hidden from us, till Almighty Allah accords him permission to reappear.
Gradings are classical jarḥ-wa-taʿdīl, name-matched to a rijāl index (not individually re-verified).