Musnad Abu Ya'la al-Mawsili 9:16

Abu Khaythama narrated to us, Abdullah ibn Numayr narrated to us, from Hajjaj, from Awn ibn Abi Juhayfah, from his father, who said: We came to the Messenger of Allah, may Allah bless him and grant him peace, among a group from Banu Amir ibn Sa'sa'ah at al-Abtah. He said, "Welcome, you are from me." When the time for prayer arrived, Bilal went out and gave the adhan. He placed his fingers in his ears and began to turn around during his adhan. When he performed the iqamah, the Prophet, may Allah bless him and grant him peace, planted a spear (anazah) and prayed facing it.