Musnad Ahmad 30:3732

Ali narrated to us, Warqa’ informed us, from Abu al-Zinad, from al-A’raj, from Abu Hurairah, who said: The Messenger of Allah (peace and blessings of Allah be upon him) said: "The Hour will not be established until knowledge is taken away, time draws near, earthquakes increase, tribulations appear, and al-harj increases." They said: "What is al-harj, O Messenger of Allah?" He said: "Killing, killing."