Musnad Ahmad 30:2792

Muhammad ibn Ja'far narrated to us, he said: Shu'bah narrated to us, from Suhayl ibn Abi Salih, from his father, from Abu Hurayrah, from the Prophet, may Allah bless him and grant him peace, that he said: "The likeness of the mujahid in the way of Allah is the likeness of the one who stands (in prayer) and does not slacken, and the likeness of the one who fasts and does not break his fast, until the mujahid in the way of Allah, the Almighty and Majestic, returns."