Usul al-Kafi
Book 5:
The Book of Belief and Disbelief

Chapter 21
Supplement of previous chapter

644. 2. Imam Jafar as-Sadiq (p): There are ten degrees of belief in ascending order. The believer who is on a higher level should not look down and underestimate the one who is at a lower level. If you see someone at a lower level, be polite to him and try to lift him up to your level and do not over-burden him with what he cannot bear, otherwise his belief will falter and then it will be your responsibility to restore it.(B5,C21,T2)