Caution: Translations of Quran and Ḥadīth may lead to possible misapplications and misinterpretations. This site is intended for students of sacred knowledge that are proficient in comprehending classical Arabic and have a strong foundation in Islamic sciences. Also note that religious injunctions rely on several aspects beyond what one may glean through reading individual aḥādīth.
darimi:1234Muḥammad b. Yūsuf > Sufyān > ʿAwn b. Abū Juḥayfah from his father > Raʾá Bilāl Adhhan

[Machine] "Thus, I made it a habit to follow his mouth movements here and there with the adhan."  

الدارمي:١٢٣٤أَخْبَرَنَا مُحَمَّدُ بْنُ يُوسُفَ حَدَّثَنَا سُفْيَانُ عَنْ عَوْنِ بْنِ أَبِي جُحَيْفَةَ عَنْ أَبِيهِ أَنَّهُ رَأَى بِلَالًا أَذَّنَ قَالَ

«فَجَعَلْتُ أَتْبَعُ فَاهُ هَاهُنَا وَهَاهُنَا بِالْأَذَانِ»  


See similar narrations below:

Collected by Bukhārī
bukhari:634Muḥammad b. Yūsuf > Sufyān > ʿAwn b. Abū Juḥayfah from his father

My father said, "I saw Bilal turning his face from side to side while pronouncing the Adhan for the prayer."  

البخاري:٦٣٤حَدَّثَنَا 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