سورة Al-Imran ( The Famiy of Imran ) - الآية 20

So if they dispute with thee, say: 'I have surrendered my will to God, and whosoever follows me. And say to those who have been given the Book and to the common folk: 'Have you surrendered?' If they have surrendered, they are right guided; but if they turn their backs, thine it is only to deliver the Message; and God sees His servants.