Musnad Ahmad 30:1712

Muhammad ibn al-Sabbah narrated to us, he said: Isma'il—meaning ibn Zakariyya—narrated to us, from Suhayl, from his father, from Abu Hurayrah, who said: The Messenger of Allah (peace and blessings of Allah be upon him) said: "The Hour will not be established until the land of the Arabs returns to being meadows and rivers, and until a rider travels between Iraq and Makkah, fearing nothing except losing the way. And until *al-harj* becomes widespread." They said: "And what is *al-harj*, O Messenger of Allah?" He said: "Killing."