Musnad Ahmad 27:979

'Affan narrated to us, 'Abd al-'Aziz ibn Muslim narrated to us, 'Abdullah ibn Dinar narrated to us, from 'Abdullah ibn 'Umar, who said: I saw the Messenger of Allah, peace and blessings of Allah be upon him, pointing toward the east and saying: "Verily, the tribulations are here; verily, the tribulations are here, from where the horn of Satan rises."