Musnad Ahmad 624:2

'Abd al-Samad narrated to us, Hammam narrated to us, 'Asim ibn Bahdalah narrated to us, Zirr ibn Hubaysh narrated to me, he said: I arrived [in Medina] during the caliphate of 'Uthman ibn 'Affan, and nothing prompted me to arrive except to meet Ubayy ibn Ka'b and the companions of the Messenger of Allah, may Allah bless him and grant him peace. So I met Safwan ibn 'Assal, and I said to him: "Did you see the Messenger of Allah, may Allah bless him and grant him peace?" He said: "Yes, and I went on twelve military expeditions with him."