Musannaf Ibn Abi Shayba 28:754

Waki’ narrated to us, he said: Abu al-Umays narrated to us, from al-Qasim ibn Abd al-Rahman, from Masruq, he said: When the two armies or the two ranks meet, there is no *nafal* (extra spoils). It is only the *ghanimah* (general spoils). The *nafal* is only before [the battle] and after [the battle].