Dr. Mustafa Khattab, the Clear Quran - Surah Al-Anfal, ayah 35

Translation of Surah Al-Anfal, ayah 35 (8:35)

وَمَا كَانَ صَلَاتُهُمۡ عِندَ ٱلۡبَيۡتِ إِلَّا مُكَآءٗ وَتَصۡدِيَةٗۚ فَذُوقُواْ ٱلۡعَذَابَ بِمَا كُنتُمۡ تَكۡفُرُونَ ٣٥
Their prayer at the Sacred House was nothing but whistling and clapping. So taste the punishment for your disbelief.