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

Chapter 25
Two kinds of Imams

352. 2. Imam Jafar as-Sadiq (p): The Imams are of two kinds. God, the Exalted, the Magnificent, says: And We appointed them to be Imams guiding by Our command… (Q, 21:73); not by the command of the people. They (the Imams) give priority to the command and ruling of God over the command and ruling of the people. And about the other kind of Imams, God says: And We appointed them to be Imams, calling to the Fire… (Q, 28:41). They gave priority to their command over the command of God, and to their ruling over the ruling of God. They follow their own desires as opposed to what is in the Noble Quran.