Who is Abd Umar from The Source; a Novel and what is their importance?

Abd Umar is also an Arab leader of a squadron of raiders in 635. He is the son of a slave and grows up in Yathrib. He is assigned to capture Makor as non-violently as possible. His purpose is to spread the dominion of Islam. In Yathrib, Abd Umar helped defend the Prophet Muhammad. He takes Makor without a battle.