The Book of Occultation — al-Ṭūsī · Hadith 421 (#Ḥadīth #22)
Chapter 34 | Evidence of the Birth of the Master of the Age
212- وروى علان بإسناده أن السيد عليه السلام ولد في سنة ست وخمسين ومائتين من الهجرة بعد مضي أبي الحسن بسنتين.
H 212 - It is narrated from Allaan Razi that he said: “The Master was born in the year two hundred and fifty-six after Hijrat, two years after the demise of Imam Ali Naqi .”
Gradings are classical jarḥ-wa-taʿdīl, name-matched to a rijāl index (not individually re-verified).