Sahih Bukhari Volume 8, Book 81, Hadith Number 777.

Narrated By ‘Aisha : Whenever the Prophet was given an option between two things, he used to select the easier of the tow as long as it was not sinful; but if it was sinful, he would remain far from it. By Allah, he never took revenge for himself concerning any matter that was presented to him, but when Allah’s Limits were transgressed, he would take revenge for Allah’s Sake.