Sahih Bukhari
Fighting for the Cause of Allah (Jihaad)
Volume: 004 / Book Number: 052 / Hadith Number: 311
Narrated Ibn 'Abbas:
The Prophet said, on the day of the Conquest of Mecca, "There is no migration (after the Conquest), but Jihad and good intentions, and when you are called for Jihad, you should immediately respond to the call."