The Book of Occultation — al-Ṭūsī · Hadith 417 (#Ḥadīth #18)
Chapter 34 | Evidence of the Birth of the Master of the Age
قال حنظلة: فدعوت بأبي الفرج المظفر بن أحمد حتى سمع معي (منه) هذا الخبر.
Hanzala, the narrator of this report says: I called Abul Faraj Muzaffar bin Ahmad and he also heard this story with me.
Gradings are classical jarḥ-wa-taʿdīl, name-matched to a rijāl index (not individually re-verified).