Surah Al-Anfal (الأنفال) Ayah 35 - Tafsir

وَمَا كَانَ صَلَاتُهُمْ عِندَ ٱلْبَيْتِ إِلَّا مُكَآءًۭ وَتَصْدِيَةًۭ ۚ فَذُوقُوا۟ ٱلْعَذَابَ بِمَا كُنتُمْ تَكْفُرُونَ

"And their prayer at the House was not except whistling and handclapping. So taste the punishment for what you disbelieved."