Musnad Ahmad 26:291

Mu'awiyah ibn 'Amr narrated to us, Za'idah narrated to us, from al-A'mash, from Shaqiq, who said: I was sitting with 'Abdullah and Abu Musa, and they were talking. They said: The Messenger of Allah, may Allah bless him and grant him peace, said: "Before the Hour, there are days in which knowledge will be lifted, ignorance will descend, and al-harj will appear." And al-harj is killing.