(Lo! they who subdue their voices in the presence of the messenger of Allah…) [49:3].
‘Ata’ reported that Ibn ‘Abbas said: “When the words of Allah (Lift not up your voices above the voice of the Prophet) were revealed, Abu Bakr vowed not to address the Messenger of Allah, Allah bless him and give him peace, except in whisper. Allah, exalted is He, revealed about Abu Bakr (Lo! they who subdue their voices in the presence of the messenger of Allah…)”.
Abu Bakr al-Qadi informed us> Muhammad ibn Ya‘qub> Muhammad ibn Ishaq al-Saghani> Yahya ibn ‘Abd al-Hamid> Husayn ibn ‘Umar al-Ahmasi> Mukhariq> Tariq> Abu Bakr who said: “When the verse (Lo! they who subdue their voices in the presence of the messenger of Allah, those are they whose hearts Allah hath proven unto righteousness) was revealed, Abu Bakr said: ‘I vowed not to address the Messenger of Allah, Allah bless him and give him peace, except in whisper’ ”.
Asbab Al-Nuzul by Al-Wahidi , trans. Mokrane Guezzou