Surah Aal-i-Imraan

Translation

So if they argue with you, say, "I have submitted myself to Allah [in Islam], and [so have] those who follow me." And say to those who were given the Scripture and [to] the unlearned, "Have you submitted yourselves?" And if they submit [in Islam], they are rightly guided; but if they turn away - then upon you is only the [duty of] notification. And Allah is Seeing of [His] servants.