Musnad Ahmad 30:2520

Yahya narrated to us, Muhammad narrated to us, Abu Salamah narrated to me, from Abu Hurairah, from the Prophet, peace and blessings of Allah be upon him, who said: "The likeness of the Mujahid in the way of Allah, the Almighty and Majestic, is like the likeness of the devout one who fasts in his house, who does not slacken, until he returns with what he returns with of spoils, or Allah takes his soul, so He enters him into Paradise."