Abu’l-Salt al-Hawawi has reported: when Imam al-Rida arrived in Nayshabur on a black and white mule, I was accompanying him and the scholars of Nayshabur had come to say welcome to the Imam. When he left to the neighborhood of Marbaeh, they took the rein of his mule saying, “O son of Allah’s Messenger! We ask you through the mediation of your purified forefathers, tell us a hadith.” Imam al-Rida who had a cloak of fur on, put his head out of the mule litter saying:
Quoting Allah’s Messenger, my father reported: Gabriel informed me of Allah saying. I am verily Allah; there is no god but Me. O My servants! Worship only Me and know that anyone of you who meets Me by bearing witness that there is no god but Allah wholeheartedly and with devotion has entered My fortress; and whoever enters My fortress will be immune from My chastisement.
They asked, “O son of Allah’s Messenger! What is devotion in the Oneness of Allah?” The Imam answered, “Obeying Allah, obeying Allah’s Messenger and obeying the Imamate of Ahl al-Bayt.” ( Al-Amali by Shaykh al-Tusi, 588, H 1220.)