Musnad Ahmad 1272:5

Abu Usamah narrated to us, he said: Hatim ibn Abi Saghirah informed me, from Simak ibn Harb, from Abu Salih, the freed slave of Umm Hani, from Umm Hani, she said: I asked the Messenger of Allah, may Allah bless him and grant him peace, about the saying of Allah the Exalted: "And you commit evil in your gatherings" [Al-Ankabut: 29]. He said: "They used to throw pebbles at those passing by on the road and mock them, and that is the evil which they used to commit."