Qur'ān 8:35 · Al-Anfal (الأنفال)

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.