8:35
Their prayer at the House (of Allah) is nothing but whistling and clapping of hands: (Its only answer
can be), “Taste ye the penalty because ye blasphemed.”
Asad explains that the phrase refers to acts that are devoid of genuine spiritual substance. Some early authorities reported that pre-Islamic Arabs performed rituals around the Kaʿbah that included dancing accompanied by whistling and hand-clapping. While this historical explanation is considered plausible, Asad suggests that the expression may also function metaphorically within the Qur’anic context. In this interpretation, “whistling and clapping of hands” symbolize the spiritual emptiness of religious practices performed without sincere devotion, particularly when people attribute quasi-divine power to worldly factors such as wealth, authority, social standing, or fortune (Asad, 1980).
References:
Asad, Muhammad (1980). The Message of the Quran.