The Book of Occultation — al-Ṭūsī · Hadith 209 (#Ḥadīth #14)

فإن قيل: فيجب على هذا أن يكون كل من لم يظهر له الإمام يقطع على أنه على كبيرة يلحق بالكفر لأنه مقصر على ما فرضتموه فيما يوجب غيبة الإمام عنه ويقتضي فوت مصلحته فقد لحق الولي على هذا بالعدو.

If it should be said: According to this, everyone to whom the Imam has not appeared should be certain that he is committing a major sin, which is an extension of disbelief (Kufr), because he is guilty, according to what you have presumed him to be, with respect to the occultation of the Imam and his loss of what is beneficial for him; this makes the devotee of the Imam his enemy.

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