Ibn Umar narrated that the Messenger of Allah said: ‘I have been commanded to fight the people until they testify that there is no god but Allah and that Muhammad is the Messenger of Allah, and establish prayer and give zakat. If they do that, their blood and wealth are protected from me except by the right of Islam, and their account is with Allah.’
Sahih Bukhari – Book of Faith – Chapter: If they repent and establish prayer and give zakat, then leave their way
http://hadith.al-islam.com/Display/Display.asp?Doc=0&Rec=44
