Musnad Ahmad 907:69

Muhammad ibn Ja'far narrated to us, Shu'bah narrated to us, from Sulayman, who said: I heard al-Musayyib ibn Rafi' narrating from Tamim ibn Tarafah, from Jabir ibn Samurah, from the Prophet, peace and blessings of Allah be upon him, that he came out to his companions and said: "What is the matter with me that I see you in groups?" while they were sitting.