Musannaf Ibn Abi Shayba 3:997

Shababa narrated to us, he said: Qays narrated to us, from Ziyad ibn 'Alaqah, from 'Umarah ibn Aws, who said: We were praying towards Bayt al-Maqdis when someone came to us while our Imam was bowing and we were bowing. He said: "Indeed, the Quran has been revealed to the Messenger of Allah (may Allah bless him and grant him peace), and he has been commanded to face the Kaaba, so be aware and face it." He said: So our Imam turned while he was bowing, and the people turned until they faced the Kaaba. Thus, we prayed part of that prayer towards Bayt al-Maqdis and part of it towards the Kaaba.