Musnad Ahmad 1034:66

Yahya ibn Abi Bukayr narrated to us, Ubayd Allah ibn Iyad ibn Laqit narrated to us, he said: I heard my father mentioning, from Hudhayfah, he said: The Messenger of Allah (peace and blessings of Allah be upon him) was asked about the Hour, and he said: "Its knowledge is with my Lord; none shall reveal it at its time except Him. But I will inform you of its signs and what will be before it. Indeed, before it there will be *fitnah* (tribulation) and *harj*." They said: "O Messenger of Allah, we have known the *fitnah*, but what is the *harj*?" He said in the Abyssinian language: "Killing. And estrangement will be cast among the people, such that hardly anyone will know anyone else."