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

Chapter 34
Hope for the best from God

685. 1. Prophet Muhammad (p) in a divine tradition said that God said: Some people do not rely on My reward for their actions (good deeds). If these people strive for their whole lives in worshipping Me, they will not be successful and will not attain any depth in My worship which will entitle them to My rewards and blessings and the bounties of My Paradise. All this will not be available without My mercy. Therefore, people ought to be afraid of Me and hope for My mercy and expect good from Me. Then they will be happy and content. My mercy will help them and My pleasure, My forgiveness and My pardon will save them …(B5,C34,T1)

686. 4. Imam Jafar as-Sadiq (p): Optimism in respect of God is that one should hope for the best from Him and must refrain from committing sins.(B5,C34,T4)