Sahih Bukhari
Afflictions and the End of the World
Volume: 009 / Book Number: 088 / Hadith Number: 185
Narrated Abu Musa:
The Prophet said, "Near the establishment of the Hour there will be days during which (religious) knowledge will be taken away (vanish) and general ignorance will spread, and there will be Al-Harj in abundance, and Al-Harj means killing."