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 Iman should be concerned with the Laws of Islam
حَدَّثَنَا أَبُو بَكْرِ بْنُ أَبِي شَيْبَةَ، حَدَّثَنَا عَبْدُ الأَعْلَى، عَنْ مَعْمَرٍ، عَنِ الزُّهْرِيِّ، عَنْ سَالِمٍ، عَنِ ابْنِ عُمَرَ، أَنَّهُمْ كَانُوا يُضْرَبُونَ عَلَى عَهْدِ رَسُولِ اللَّهِ صلى الله عليه وسلم إِذَا اشْتَرَوْا طَعَامًا جِزَافًا أَنْ يَبِيعُوهُ فِي مَكَانِهِ حَتَّى يُحَوِّلُوهُ .
Ibn 'Umar (Allah be pleased with them) reported that they were beaten during the lifetime of Allah's Messenger (ﷺ) if they had bought foodgrains in bulk and then sold them in the spot without shifting them (to some other place).
Reference: Sahih Muslim 1527 c In-book : Book 21, Hadith 45 USC-MSA web (English) : Book 10, Hadith 3649 (deprecated)
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