Sahih Muslim
The Book of Faith (Kitab Al-Iman)
Book Number: 001 / Hadith Number: 30
It is reported on the authority of Abu Huraira that the Messenger of Allah said: I have been commanded to fight against people so long as they do not declare that there is no god but Allah, and he who professed it was guaranteed the protection of his property and life on my behalf except for the right affairs rest with Allah.