From AlHasan son of Ali AlWasha(companion of Imam Ritha pbuh)and he has left from being a Waqifi(believing that Musa AlKathem a.s. is the Qaim and no Imam after him)from unseen news that Imam Ritha pbuh showed him.
He said:(We were with a man in Maro and there was with us a man who was a Waqifi so I said to him: Fear Allah, I used to be like you so Allah illuminated my heart. So fast Wednesday, Thursday and Friday and make Gusel and pray 2 rakaat and ask Allah so that he can show you in your sleep of what can be evidence to this matter. So I returned to the house and a book from Abi AlHasan already reached me and he was ordering me to make dua about this matter for that man. So I went to him and reported him. And I said: Praise Allah and >>make Istikhara 100 times<<. And I said to him: I found the book of Abi AlHasan which reached me to the house to say to you about what we were in. And I hope that Allah will illuminate your heart. So do what I told you from fasting and dua, so he came to me on the day of Saturday at night. So he said to him: I bear witness that he is the Imam who is obligatory to obey. So I said: How? So he said: Abu AlHasan pbuh came to me in sleep and said: O Ibraheem by Allah you will return to the truth, and he claimed that no one showed him except Allah.)
AlKhara’ej Wal Jara’eh v.1 p.366 h.23
Bihar AlAnwar v.49 p.53 h.6
Awaalem v.22 p.104 h.78