Abu Wa'il says that once Sayyiduna Ibn Mas'ud (may Allah be pleased with him) and Sayyiduna Abu Musa Ash'ari (may Allah be pleased with him) said that the Messenger of Allah (peace and blessings be upon him) said: "Near the Day of Judgment, ignorance will descend, knowledge will be taken away, and there will be an abundance of 'harj'." We asked about the meaning of 'harj', so he said: "Killing."