Kitab al-Kafi
In Kitab al-Kafi, Ja'far al-Sadiq writes a letter to his companions stressing the importance of obeying Allah, his Messenger, and the "Wali al Amr" (Progeny of Muhammad)- going so far as to say that those who disobey and deny their virtues are "liars and hypocrites". He asserts that these are the individuals described as "hypocrites" in the verse, "Indeed, the hypocrites will be in the lowest depths of the Fire - and never will you find for them a helper."