Musnad Abu Ya'la al-Mawsili 108:212

Zakariya ibn Yahya narrated to us, he said: Hushaym narrated to us, from Husayn, from Salim ibn Abi al-Ja’d and Abu Sufyan, from Jabir ibn Abdullah, who said: While the Prophet, peace and blessings of Allah be upon him, was delivering the sermon on Friday, a caravan arrived in Medina. The companions of the Messenger of Allah, peace and blessings of Allah be upon him, rushed toward it until there remained with him only twelve men. The Messenger of Allah, peace and blessings of Allah be upon him, said: "By the One in Whose hand is my soul, if you had followed one another until not one of you remained, the valley would have flowed with fire for you." Then this verse was revealed: "And when they see a transaction or a diversion, they disperse toward it and leave you standing" (Al-Jumu'ah). And he mentioned among the twelve who remained with the Messenger of Allah, peace and blessings of Allah be upon him, Abu Bakr and Umar.