It is narrated on the authority of 'Abdullah bin 'Umar (RA) who narrates from the Prophet (ﷺ) of Allah (ﷺ) who said: He who took up arms against us is not of us.
Hadith ReferenceSahih Muslim / The Book of Faith / Hadith: 98
Hadith Gradingمحدثین:أحاديث صحيح مسلم كلها صحيحة
Hadith Takhrij«أحاديث صحيح مسلم كلها صحيحة ، انفرد به مسلم - انظر ((التحفة)) برقم (8003)»