Imam Malik's Muwatta, Chapter: Madina

Yahya related to me from Malik from Ibn Shihab that the Messenger of Allah, may Allah bless him and grant him peace, said, "Two deens shall not co-exist in the Arabian Peninsula." Malik said that Ibn Shihab said, ''Umar ibn al-Khattab searched for information about that until he was absolutely convinced that the Messenger of Allah, may Allah bless him and grant him peace, had said, 'Two deens shall not co-exist in the Arabian Peninsula,' and he therefore expelled the jews from Khaybar."