Musnad Ahmad 27:1726

Ya'qub narrated to us, my father narrated to us, from Salih, Ibn Shihab said: Salim ibn Abdullah informed me that Abdullah ibn Umar said: I heard the Messenger of Allah, may Allah bless him and grant him peace, saying: "The Jews will fight you, and you will be given power over them, until the stone says: 'O Muslim, this is a Jew behind me, so kill him.'"