Sayyiduna Nu'man bin Bashir (may Allah be pleased with him) narrates this saying of the Prophet (peace and blessings be upon him): "I have been commanded to fight people until they say La ilaha illallah (there is no god but Allah). When they say it, they will have secured their lives and their wealth from me, except by its right."
Al-Bazzar recorded it, and its narrators are the narrators of the Sahih.
Hadith Referenceمجمع الزوائد ومنبع الفوائد / كتاب الإيمان / 57