Musnad Ahmad 30:1862

'Affan narrated to us, 'Abd al-Wahid narrated to us, 'Amarah narrated to us, Abu Zur'ah narrated to us, that he heard Abu Hurayrah say: The Messenger of Allah (peace and blessings of Allah be upon him) said: "By the One in Whose hand is my soul, I would love to fight in the way of Allah and be killed, then fight and be killed, then fight and be killed."