 Since the Constitution of Medina, drafted by the Islamic prophet Muhammad, the Jews and the Christians continued to use their own laws and had their own judges.To assist in the quick expansion of the state, the Byzantine and the Persian tax collection systems were maintained and the people paid a poll tax lower than the one imposed under the Byzantines and the Persians.In 639, Umar appointed Muawiyah ibn Abi Sufyan as the governor of Syria after the previous governor died in a plague along with 25,000 other people.