Surah Al-Hujurat, Verse 3

إِنَّ ٱلَّذِينَ يَغُضُّونَ أَصۡوَٰتَهُمۡ عِندَ رَسُولِ ٱللَّهِ أُوْلَٰٓئِكَ ٱلَّذِينَ ٱمۡتَحَنَ ٱللَّهُ قُلُوبَهُمۡ لِلتَّقۡوَىٰۚ لَهُم مَّغۡفِرَةٞ وَأَجۡرٌ عَظِيمٌ٣

inna alladhīna yaghuḍḍūna aṣwātahum ʿinda rasūli l-lahi ulāika alladhīna im'taḥana l-lahu qulūbahum lilttaqwā lahum maghfiratun wa-ajrun ʿaẓīmun

Indeed, those who lower their voices before the Messenger of Allāh - they are the ones whose hearts Allāh has tested for righteousness. For them is forgiveness and great reward.