Majma al-Zawaid — Hadith 11024

Sayyiduna Ubadah bin al-Samit (may Allah be pleased with him) narrates: We set out with the Prophet (peace and blessings be upon him) and took part with him in the Battle of Badr. When the two sides met, Allah Almighty routed the enemy. One group (of the Muslims) went after the enemy to rout them and kill them; one group busied itself with collecting (the belongings of) the camp and gathering them; and one group came to the Prophet (peace and blessings be upon him) so that the enemy would not take him unawares and harm him. When night came and the people rejoined one another, those who had collected the spoils said: "We collected it and gathered it, so no one else has any share in it." Those who had gone after the enemy said: "You have no greater right to it than we do; we drove the enemy away from it and routed them." Those who had been guarding the Prophet (peace and blessings be upon him) said: "You have no greater right to it than we do. We guarded the Prophet (peace and blessings be upon him); we feared that the enemy might take him unawares and harm him, and we were occupied with that." Then this verse was revealed concerning this: "They ask you about the spoils (anfal). Say: The spoils belong to Allah and the Messenger, so fear Allah and set right matters between you." So the Prophet (peace and blessings be upon him) divided that wealth among all the Muslims on an equal basis. When the Prophet (peace and blessings be upon him) raided enemy land, he would give a quarter as a bonus (nafl), and when he was returning and the people were exhausted, he would give a third as a bonus. He himself disliked (taking) the spoils, and he used to say: "Let the strong among the believers give back to their weak."
(Allamah al-Haythami says:) I say: Imam al-Tirmidhi and Imam Ibn Majah recorded from this report only that the Prophet (peace and blessings be upon him) used to give a quarter as a bonus at the outset and a third on the return.
Imam Ahmad recorded it.