Surah Al-Hujurat 49:3

إِنَّ ٱلَّذِينَ يَغُضُّونَ أَصْوَٰتَهُمْ عِندَ رَسُولِ ٱللَّهِ أُو۟لَـٰٓئِكَ ٱلَّذِينَ ٱمْتَحَنَ ٱللَّهُ قُلُوبَهُمْ لِلتَّقْوَىٰ ۚ لَهُم مَّغْفِرَةٌ وَأَجْرٌ عَظِيمٌ

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.

Translation: Saheeh International

Tafsir

The following was revealed regarding those who used to lower their voices in the presence of the Prophet s such as Abū Bakr ‘Umar and others may God be pleased with all of them Truly those who lower their voices in the presence of God’s Messenger — they are the ones whose hearts God has tested for God-fearing that is …

Excerpt from Tafsir al-Jalalayn, commentary on 49:3, via Quran.com. The reader has the full commentary and 9 more tafsirs.