Musnad Abu Ya'la al-Mawsili 50:4

Abu Bakr narrated to us, Ibn Mubarak and Waki’ narrated to us, from Isma’il, from Qays, from al-Sanabahi, from the Prophet (may Allah bless him and grant him peace), who said: "I am a forerunner for you at the Basin (al-Hawd), and I will boast of your great numbers against the nations. So do not fight one another after me."