Umar
Free trade

Local populations of Jews and Christians, persecuted as religious minorities and taxed heavily to finance the Byzantine–Sassanid Wars, often aided Muslims to take over their lands from the Byzantines and Persians, resulting in exceptionally speedy conquests. As new areas were attached to the Caliphate, they also benefited from free trade, while trading with other areas in the Caliphate (to encourage commerce, in Islam trade is not taxed, but wealth is subject to the zakat). Since the Constitution of Medina, drafted by Muhammad, the Jews and the Christians continued to use their own laws in the Caliphate and had their own judges.
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