How did early Muslims run the state of affairs? Zakat is for the poor as there are 8 categories of people who can receive Zakat. Therefore, Zakat cannot be equated to State Tax. So how did 7th century Muslims finance their wars and governance? What was their economy based on? Spoils of war? For which the Quran has given detailed injunctions. Slave trade? Yes. Jizya? which is non-Muslim tax. If one doesn't give Zakat, is there any punishment? I couldn't find a worldly one. So it's a personal matter between a Muslim and Allah. That also means it is voluntarily obligatory just like Namaz, Roza and Haj.

How is jizya and spoils of war relevant in the present age? Mind it that slave trade is also part of the spoils of war.

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He that increaseth knowledge increaseth sorrow (Ecclesiastes 1:18)