The Book of Occultation — al-Ṭūsī · Hadith 628 (#Ḥadīth #7)
Chapter 47 | False claimants of deputyship of Imam who are also clearly condemned by the Imams
372- أخبرني بذلك عن محمد بن نصير أبو زكريا يحيى بن عبد الرحمن بن خاقان أنه رآه عيانا وغلام له على ظهره قال: فلقيته فعاتبته على ذلك فقال إن هذا من اللذات وهو من التواضع لله وترك التجبر.
H 372 - It is narrated on the authority of Muhammad Ibn Nasir Abu Zakariya Yahya Ibn Abdur Rahman Ibn Khaqan, that he clearly saw him with a boy over his back. He said: I met him and rebuked him for that. He said: “It is of the pleasures and humility for Allah and abstinence from arrogance.”
Gradings are classical jarḥ-wa-taʿdīl, name-matched to a rijāl index (not individually re-verified).