Sahih Bukhari Volume 4, Book 52, Hadith Number 176.

Narated By ‘Abdullah bin ‘Umar : Allah’s Apostle said, “You (i.e. Muslims) will fight wi the Jews till some of them will hide behind stones. The stones will (betray them) saying, ‘O ‘Abdullah (i.e. slave of Allah)! There is a Jew hiding behind me; so kill him.'”