It is narrated from Abu Hurairah (may Allah be pleased with him) that the Messenger of Allah (peace and blessings be upon him) said: "I will continue to fight against the people until they testify that there is no deity except Allah. When they do so, they will have protected their blood and their wealth from me, except for its due right, and their reckoning is with Allah."
Hadith Referenceمسند الإمام الشافعي / كتاب الجهاد وقسم الغنائم / 1726
Hadith Takhrijاخرجه البخارى الجهاد والسير، باب دعاء النبي الى الاسلام والنبوة .... الخ (2946) ۔ مسلم، الايمان، باب الأمر بقتال الناس حتى يقولوا لا اله الا الله..... الخ (21)۔