The meaning of the Shield of Allah, Exalted and Glorious is He

When Abu’l-Hasan al-Rida, peace be upon him, arrived at Nishapur and wanted to get out of it (in order to journey) to al-Ma’mun, the people of narrations gathered to him and said: O son of Allah’s Messenger, will you depart from us and not tell us of a narration, by which we may benefit of it from you? He was sitting in ‘Amariya, and so he raised his head and said: I heard my father, Musa bin Ja’far, say: I heard my father, Ja’far bin Muhammed, say: I heard my father, Muhammed bin Ali, say: I heard my father, Ali bin Hussain, say: I heard my father, Hussain bin Ali bin Abi Talib, say: I heard my father, the Commander of the Believers, Ali bin Abi Talib, peace be upon them, say: I heard the Messenger of Allah, Allah’s blessings be upon him and his Family, say: I heard Jibra’eel, peace be upon him, say: I heard Allah, Exalted and Glorious is He, say: «There is no god but Allah» is My Shield. Hence, the one who enters My Shield is safe from My punishment. He said: Then, when the caravan walked, he called to us: With its conditions, and I am one of its conditions.