Surah 8. Al-Anfal, Ayah 35

I.e., devoid of all spiritual contents. Some of the early authorities maintain that dancing around the Ka'bah, accompanied by whistling and hand-clapping, was actually a ritual practiced by the pre-Islamic Arabs. Although this explanation is quite plausible, it would appear from the context that the expression "whistling and clapping of hands" is used here metaphorically, to denote the spiritual emptiness of the religious rituals of people who are wont to attribute a quasi-divine efficacy to all manner of circumstantial "forces" - like wealth, power, social status, "luck", etc.

The chastisement or suffering referred to here was their crushing defeat at Badr.