Musannaf Ibn Abi Shayba 18:601

Abu Bakr narrated to us, he said: Humayd ibn Abd al-Rahman narrated to us, from Hasan, from Mutarrif, from al-Hakam, who said: Umar said: "The first to make the blood money (diyah) ten by ten (in installments) was among the stipends of the fighters, not the (rest of the) people."