Musnad Ahmad 33:241

Ibn Idris narrated to us, from Husayn, from Salim ibn Abi al-Ja'd, from Jabir, who said: "A caravan arrived in Medina while the Messenger of Allah, may Allah bless him and grant him peace, was delivering the sermon. The people went out, and twelve remained. Then it was revealed: 'And when they saw a transaction or a diversion, they dispersed to it' [Al-Jumu'ah: 11]."