Musannaf Ibn Abi Shayba 36:127

'Abd al-A'la ibn 'Abd al-A'la narrated to us, from Dawud, from 'Ikrimah, from Ibn 'Abbas, who said: When the day of Badr arrived, the Messenger of Allah (peace and blessings of Allah be upon him) said: "Whoever does such and such, for him is such and such." He said: The young men rushed to that, while the elders remained under the banners. When the spoils of war arrived, they came seeking what had been promised to them. The elders said: "Do not take it all for yourselves, for we were your support and we were under the banners; if you had been defeated, you would have retreated to us." They disputed, so Allah revealed: "They ask you about the spoils of war," up to His saying: "And obey Allah and His Messenger, if you are believers."