Musannaf Ibn Abi Shayba 18:853

Abu Bakr narrated to us, he said: Hafs narrated to us, from Hajjaj, from al-Hakam, from Miqsam, from Ibn Abbas, he said: The Messenger of Allah (may Allah bless him and grant him peace) wrote a document between the Emigrants (Muhajirun) and the Helpers (Ansar) that they should pay their blood-monies (diya) collectively, and that they should ransom their captives with kindness and reconciliation among the Muslims.