Sahih Bukhari Volume 1, Book 2, Hadith Number 19

Narated By ‘Aisha : Whenever Allah’s Apostle ordered the Muslims to do something, he used to order them deeds which were easy for them to do, (according to their strength endurance). They said, “O Allah’s Apostle! We are not like you. Allah has forgiven your past and future sins.” So Allah’s Apostle 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.”