Sahih Muslim Book 19, Hadith Number 4292.

Chapter : Regarding permission to make a raid, without an ultimatum, upon the disbelievers who have already been invited to accept Islam.Ibn 'Aun reported: I wrote to Nafi' inquiring from him whether it was necessary to extend (to the disbelievers) an invitation to accept (Islam) before making them in fight. He wrote (in reply) to … Continue reading Sahih Muslim Book 19, Hadith Number 4292.