A Yemenite Jew who had converted to Islam, and who was regarded as an authority on Jews and Judaism. Ka`b converted in the days of the caliph Abu Bakr or after `Umar became caliph. His Hebrew name was Rabbi Aqiva/Jacob. He was also called Abu Ishaq ben Matia`. The word Ahbar means friend�a title referring to a Babylonian scholar. According to Tabari, the greatest of Arab chroniclers, Ka`b had joined Umar on his visit to Jerusalem and the Temple Mount, and it was he who assisted Umar in identifying the Foundation Stone and in deciding upon the direction of prayer. Ka`b suggested a point to the north of the Rock, so that the worshipper would at once face Mecca and the Rock. Umar immediately rejected his proposal, accusing him of imitating the Jews, and then fixed the place of prayer to the south of the Rock.

Ka`b�s support of caliph Othman in his battle against Ali resulted in his flight to Syria. Subsequently, Ka`b served as teacher in the court of caliph Mu`awiya. He died in 652/4 in Damascus.

Most of the Israelite traditions, rendering the history of the Israelite patriarchs and the Pentateuch, are assigned to Ka`b. He is also considered author of many chapters associated with praises of Jerusalem and the Temple Mount. This triggered Arab writers throughout the history of Islam to accuse him of being a Jew who thrived on inserting Jewish ideas into Islam.