Narrated 'Aun bin Abi Juhaifa:
My father said, "I saw Bilal turning his face from side to side while pronouncing the Adhan for the prayer."
حَدَّثَنَا مُحَمَّدُ بْنُ يُوسُفَ، قَالَ حَدَّثَنَا سُفْيَانُ، عَنْ عَوْنِ بْنِ أَبِي جُحَيْفَةَ، عَنْ أَبِيهِ، أَنَّهُ رَأَى بِلاَلاً يُؤَذِّنُ فَجَعَلْتُ أَتَتَبَّعُ فَاهُ هَا هُنَا وَهَا هُنَا بِالأَذَانِ.
• Sahih al-Bukhari, 634
• Sahih al-Bukhari, Vol. 1, Book of Call to Prayer, Hadith 607
• Sahih al-Bukhari, Book of Call to Prayer, Hadith 607