Fa in haaajjooka faqul aslamtu wajhiya lillaahi wa manit taba'an; wa qul lillazeena ootul Kitaaba wal ummiyyeena 'a-aslamtum; fa in aslamoo faqadih tadaw wa in tawallaw fa innamaa 'alaikal balaagh; wallaahu baseerum bil 'ibaad
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.
1 Mufti Taqi Usmani
Then, if they argue with you, say: “I have submitted myself to Allah, and (so did) those who have followed me.” And say to those who have been given the Book, and to the unlettered: “Do you submit?” If they submit, they will be on the right path. Yet, if they turn back, then you have only to convey the message. Allah is watchful over (all of) His servants.