Musnad Ahmad 765:4

'Abbad ibn 'Abbad ibn Habib ibn al-Muhallab ibn Abi Sufrah al-Muhallabi, Abu Mu'awiyah, narrated to us, from Mujalid ibn Sa'id, from Qays ibn Abi Hazim, from al-Sunabihi, who said: The Messenger of Allah (peace and blessings of Allah be upon him) said: "I will boast of your great numbers before the nations, so do not return after me as disbelievers, striking the necks of one another."