Surah Al-Anfal — Ayah 35 (8:35)
وَمَا كَانَ صَلَاتُهُمۡ عِندَ ٱلۡبَيۡتِ إِلَّا مُكَآءٗ وَتَصۡدِيَةٗۚ فَذُوقُواْ ٱلۡعَذَابَ بِمَا كُنتُمۡ تَكۡفُرُونَ ٣٥
English translation (Saheeh International)
And their prayer at the House [i.e., the Kaʿbah] was not except whistling and handclapping. So taste the punishment for what you disbelieved [i.e., practiced of deviations].
Brief commentary
The prayer of the idolaters at the Sacred Mosque was nothing but whistling and clapping. So taste, O idolaters, the punishment of being killed or taken prisoner on the day of Badr because of your disbelief in Allah and rejection of His Messenger.