Musnad Ahmad 658:10

Sulayman ibn Dawud al-Hashimi narrated to us, he said: Abu Bakr informed us, from Abu Ishaq, he said: I said to al-Bara’: "A man charges at the polytheists, is he among those who cast themselves into destruction?" He said: "No, because Allah, the Almighty and Majestic, sent His Messenger, may Allah bless him and grant him peace, and said: 'Then fight in the way of Allah; you are not held responsible except for yourself' [An-Nisa: 84]. That refers only to spending."