Salim says: I do not remember how many times I have heard Abu Hurairah (may Allah be pleased with him) standing in the market saying: Knowledge will be taken away, tribulations will appear, and killing (harj) will increase. The companions (may Allah be pleased with them) asked: O Messenger of Allah (peace and blessings be upon him), what is meant by harj? The Prophet (peace and blessings be upon him) gestured with his hand (killing, killing).
Hadith Referenceمسند احمد / مسند المكثرين من الصحابة / 7872