In Zakheerah and Tazkerah2 it is said that this is a title of the Imam in the book of Deed-e-Brahmah, which according to their belief, is a heavenly book.
It is mentioned in Tafseer Furaat bin Ibrahim Koofi3 that it is narrated from Imam Muhammad Baqir (a.s.) that he said under the explanation of the verse