Musannaf Ibn Abi Shayba 3:4284

Sahl ibn Yusuf narrated to us, from Humayd, from Anas, who said: Al-Nu'man ibn Muqarrin was over the army of the people of Kufa, and Abu Musa al-Ash'ari was over the army of Basra, and I was between them. They made an appointment to meet at my place in the morning. One of them prayed the morning prayer with his companions, then he came while I was praying, and he prayed with me.