Musannaf Ibn Abi Shayba 37:171

Abu Khalid al-Ahmar narrated to us, from Mujalid, from al-Sha'bi, from Masruq, who said: We came to Umar, and he said: "How is your livelihood?" We said: "We are the most prosperous of people, from a people who fear the Dajjal." He said: "What is before the Dajjal is more fearful to you than the Dajjal: the Harj." I said: "And what is the Harj?" He said: "The killing, until a man kills his own father."