Sahih Muslim Book 20, Hadith Number 4639.

Chapter : Merit of leaving for Jihad in the morning and evening.

It has been narrated on the authority of Anas b. Malik that the Messenger of Allah (may peace be upon him) said: Leaving (for Jihad) in the way of Allah in the morning or in the evening (will merit a reward) better than the world and all that is in it.