Sayyidina Abu Hurairah (RA) reported that Allah’s Messenger (SAW) said, "I have been commanded to fight people till they say 'There is no God but Allah'. So, if they say that then they have protected from me their blood and their property, save against a right on them, and their reckoning is with Allah.”
[Abu Dawud 2640, Nisai 29861, Bukhari 927, Ahmed 89131]