Surah Al-Hujurat (The Private Quarters), Verse 3

اِنَّ الَّذِیْنَ یَغُضُّوْنَ اَصْوَاتَهُمْ عِنْدَ رَسُوْلِ اللّٰهِ اُولٰٓىِٕكَ الَّذِیْنَ امْتَحَنَ اللّٰهُ قُلُوْبَهُمْ لِلتَّقْوٰی لَهُمْ مَّغْفِرَةٌ وَّاَجْرٌ عَظِیْمٌ ۟

Innal lazeena yaghud doona aswaatahum 'inda Rasoolil laahi ulaaa'ikal lazeenam tah anal laahu quloobahum littaqwaa; lahum maghfiratunw wa'ajrun 'azeem

“Those that lower their voices in the presence of Allah's Messenger,- their hearts has Allah tested for piety: for them is Forgiveness and a great Reward.”

Quran 49:3 (Yusuf Ali Translation)