Sahih Muslim 21 c
The Book of Faith
The command to fight the people until they say "La ilaha illallah Muhammad Rasul-Allah", and establish Salat, and pay the Zakat, and believe in everything that the prophet (ﷺ) brought. Whoever does that, his life and his wealth are protected except by its right, and his secrets are entrusted to Allah, the most high. Fighting those who withhold Zakat or other than that is one of the duties of Islam and the Imam should be concerned with the Laws of Islam
It is narrated on the authority of Jabir that the Messenger of Allah said: I have been commanded that I should fight against people till they declare that there is no god but Allah, and when they profess it that there is no god but Allah, their blood and riches are guaranteed protection on my behalf except where it is justified by law, and their affairs rest with Allah, and then he (the Prophet) recited (this verse of the Holy Qur'an):" You are not over them a warden" (88: 22).