Musannaf Ibn Abi Shayba 2:116

2233. Malik ibn Isma'il narrated to us, he said: Zuhayr narrated to us, he said: Abu Tahir al-Ju'fi narrated to us, he said: I gave the adhan several times. Suwayd said to me: "When you give the adhan, face the qibla, for it is from the Sunnah."