Sahih Bukhari Volume 001, Book 002, Hadith Number 019.
Sahih Bukhari Book 02. Belief
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."