Musnad Ahmad 788:112

Muhammad ibn Ja'far and 'Affan narrated to us, they said: Shu'bah narrated to us, from 'Amr ibn Murrah, he said: 'Affan said: 'Amr ibn Murrah informed me, he said: I heard Abu Wa'il say: Abu Musa al-Ash'ari narrated to us, that a Bedouin came to the Prophet, may Allah bless him and grant him peace, and said: "O Messenger of Allah, a man fights for spoils, a man fights to be mentioned, and a man fights to have his position seen; so who is in the way of Allah?" The Messenger of Allah, may Allah bless him and grant him peace, said: "Whoever fights so that the word of Allah may be supreme, he is in the way of Allah, the Almighty and Majestic."