Hadith: I have been commanded to fight against the people until they testify that there is no god but Allah and that Muhammad is the Messenger of Allah, and until they establish the prayer and pay Zakah. If they do so, their blood and property are guaranteed my protection, unless (they commit acts that are punishable) in accordance with Islam, and their reckoning will be with Allah, the Almighty

عَنِ ابْنِ عُمَرَ رضي الله عنهما أَنَّ رَسُولَ اللَّهِ صَلَّى اللهُ عَلَيْهِ وَسَلَّمَ قَالَ:

«أُمِرْتُ أَنْ أُقَاتِلَ النَّاسَ حَتَّى يَشْهَدُوا أَنْ لاَ إِلَهَ إِلَّا اللَّهُ، وَأَنَّ مُحَمَّدًا رَسُولُ اللَّهِ، وَيُقِيمُوا الصَّلاَةَ، وَيُؤْتُوا الزَّكَاةَ، فَإِذَا فَعَلُوا ذَلِكَ عَصَمُوا مِنِّي دِمَاءَهُمْ وَأَمْوَالَهُمْ إِلَّا بِحَقِّ الإِسْلاَمِ، وَحِسَابُهُمْ عَلَى اللَّهِ».
[صحيح] - [متفق عليه]

‘Umar ibn al-Khattāb, his son ‘Abdullāh, and Abu Hurayrah (may Allah be pleased with them) reported that the Messenger of Allah (may Allah's peace and blessings be upon him) said: "I have been commanded to fight against the people until they testify that there is no god but Allah and that Muhammad is the Messenger of Allah, and until they establish the prayer and pay the Zakah. If they do so, their blood and property are guaranteed my protection, unless (they commit acts that are punishable) in accordance with Islam, and their reckoning will be with Allah, the Almighty."
Sahih/Authentic. - [Al-Bukhari and Muslim with all its versions]

Explanation

Allah, the Almighty, ordered fighting the polytheists (who associate others with Him in worship) until they testified that there is no god but Allah alone, without partners and that Muhammad (may Allah's peace and blessings be upon him) is the Messenger of Allah, and that they perform the acts of worship that this testimony entails; the five daily obligatory prayers and Zakah when it becomes due. If they fulfill these pillars (of Islam) along with what else Allah has made obligatory for them, their lives and property become inviolable by virtue of their reversion to Islam. Excluded from such inviolability are actions that entail retribution or a prescribed punishment under the Shariah. Whoever sincerely complies with what he is commanded to do is a believer, and whoever complies out of precautionary dissimulation and fear for his life and property is a hypocrite. Allah knows his true intention and He will hold him accountable for it.