Quran Al-Hujurat 49:3
إِنَّ ٱلَّذِينَ يَغُضُّونَ أَصۡوَٰتَهُمۡ عِندَ رَسُولِ ٱللَّهِ أُوْلَٰٓئِكَ ٱلَّذِينَ ٱمۡتَحَنَ ٱللَّهُ قُلُوبَهُمۡ لِلتَّقۡوَىٰۚ لَهُم مَّغۡفِرَةٞ وَأَجۡرٌ عَظِيمٌ ٣
Translation
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.