Musnad Ahmad 30:2635

Waki’ narrated to us, he said: Hammad—meaning Ibn Salamah—narrated to us, from Muhammad, from Abu Hurairah, who said: The Messenger of Allah (peace and blessings of Allah be upon him) said: "Be, servants of Allah, brothers. Do not show enmity toward one another, and do not hate one another. Be upright, draw near [to the truth], and receive glad tidings."