Ka'ab al-Ahbar was forced to convert to Islam .
Caliph Omar ibn al Khattab ( 579-644 ) was advised by his associate , Ka'ab al-Ahbar , a Jewish rabbi who converted to Islam , Yakub of Syria ( Ka'b al-Ahbar ) Last Jewish Attempt at Islamic Leadership Committee for Historical Research in Islam and Judaism , © 2004-2012 , accessed July 2013. ``
Dome of the Rock