Sahih al-Bukhari 20

Narrated 'Aisha:

Whenever Allah's Messenger peace be upon him ordered the Muslims to do something, he used to order them deeds which were easy for them to do, (according to their strength and endurance). They said, "O Allah's Messenger peace be upon him! We are not like you. Allah has forgiven your past and future sins." So Allah's Apostle peace be upon him became angry and it was apparent on his face. He said, "I am the most Allah fearing, and know Allah better than all of you do."