Sahih Muslim Book 19, Hadith Number 4409.

Chapter : The treaty of Hudaibiya.

It has been narrated on the authority of Anas b. Malik who said: When they (Companions of the Holy Prophet) were overwhelmed with grief and distress on his return from Hudaibiya where he had slaughtered his sacrificial beasts (not being allowed to proceed to Mecca), the Qur’anic verse: Inna fatahna… laka fathan mobinan to fauzan ‘aziman, was revealed to him. (At this) he said: On me has descended a verse that is dearer to me than the whole world.