Musannaf Ibn Abi Shayba 3:5188

7565. Kathir ibn Hisham narrated to us, from Ja'far ibn Burqan, who said: I asked Maymun about praying behind the commanders, and he said: "Pray with them." Kathir ibn Hisham narrated to us, from Ja'far ibn Burqan, who said: I asked Maymun about a man, and he mentioned that he was one of the Khawarij. He said: "You do not pray for him; you only pray for Allah. We used to pray behind al-Hajjaj, and he was a Haruri, Azraqi."