The Nature of Truth and Reality (15)

3:72 Sahih International: And a faction of the People of the Scripture say [to each other], "Believe in that which was revealed to the believers at the beginning of the day and reject it at its end that perhaps they will abandon their religion,

3:73 Sahih International: And do not trust except those who follow your religion." Say, "Indeed, the [true] guidance is the guidance of Allah. [Do you fear] lest someone be given [knowledge] like you were given or that they would [thereby] argue with you before your Lord?" Say, "Indeed, [all] bounty is in the hand of Allah - He grants it to whom He wills. And Allah is all-Encompassing and Wise."

Argue with them upon the belief that Allah guides whom he wills and that they are not the only ones or the last ones to receive the guidance of Allah. 

The only way to the truth is the guidance of Allah