Musannaf Ibn Abi Shayba 3:5986

Abdullah ibn Idris narrated to us, from Muhammad ibn Ishaq, from Muhammad ibn Ja'far ibn al-Zubayr, that the Messenger of Allah (peace and blessings of Allah be upon him) sent Abdullah ibn Unays to Khalid ibn Sufyan. He said: "When I drew near to him—and that was at the time of Asr—I feared that there might be some obstruction or struggle between us, so I prayed while I was walking."