Musnad Ahmad 30:3726

'Ali narrated to us, Warqa' informed us, from Abu al-Zinad, from al-A'raj, from Abu Hurairah, who said: The Messenger of Allah (peace and blessings of Allah be upon him) said: "The Hour will not be established until you fight the Jews, until the Jew hides behind the stone, and the stone says: 'O Muslim, this is a Jew hiding behind me, so come and kill him.'"