Sahih Muslim Book 1, Hadith Number 182.

Chapter : The utterance of the Apostle (way peace be upon him). He who acted dishonestly towards us is not of us(i.e. he is not to be counted amongst Muslims).

It is narrated on the authority of Abu Huraira that the Messenger of Allah (may peace be upon him) observed: He who took up arms against us is not of us and he who acted dishonestly towards us is not of us.