Usul al-Kafi
Book 4:
The Book of Divine Proof

Chapter 24
The inheritors of the book

350. 1. Imam Muhammad al-Baqir (p) was requested to explain the meaning of the verse: Then We have given the Book in inheritance to such of our servants as We have chosen. There are among them some who wrong their own souls, some who are moderate and some who are by God’s leave, foremost in good deeds; that is the highest grace. (Q, 35:32)
The Imam (p): Foremost in good deeds are the Imams (p). The moderates are those who recognize their Imams and the wrongdoers are those who do not recognize the Imams.

351. 4. Imam Jafar as-Sadiq (p) was requested to explain the meaning of the verse: Those to whom We sent the Book recite it as it should be recited, they are the ones who are the real believers… (Q, 2:121)
The Imam (p): They are the Imams.