Sura al-Ḥujurāt 49:2

يَٰٓأَيُّهَا ٱلَّذِينَ ءَامَنُوا۟ لَا تَرْفَعُوٓا۟ أَصْوَٰتَكُمْ فَوْقَ صَوْتِ ٱلنَّبِىِّ وَلَا تَجْهَرُوا۟ لَهُۥ بِٱلْقَوْلِ كَجَهْرِ بَعْضِكُمْ لِبَعْضٍ أَن تَحْبَطَ أَعْمَٰلُكُمْ وَأَنتُمْ لَا تَشْعُرُونَ

yā-ayyuhā lladhīna āmanū lā tarfaʿū aṣwātakum fawqa ṣawti l-nabiyyi wa-lā tajharū lahu bil-qawli kajahri baʿḍikum li-baʿḍin an taḥbaṭa aʿmālukum wa-antum lā tashʿurūna

O ye who believe! Raise not your voices above the voice of the Prophet, nor speak aloud to him in talk, as ye may speak aloud to one another, lest your deeds become vain and ye perceive not.

Sura al-Mulk 67:13

وَأَسِرُّوا۟ قَوْلَكُمْ أَوِ ٱجْهَرُوا۟ بِهِۦٓ إِنَّهُۥ عَلِيمٌۢ بِذَاتِ ٱلصُّدُورِ

wa-asirrū qawlakum awi ijharū bihi innahu ʿalīmun bi-dhāti l-ṣudūri

And whether ye hide your word or publish it, He certainly has (full) knowledge, of the secrets of (all) hearts.