47.Behold, one truly an Israelite. It is not on Nathanael’ own account that Christ bestows on him this commendation, but under his person he holds out a general doctrine. For, since many who boast of being believers are very far from being actually believers, it is of great importance that some mark should be found for distinguishing the true and genuine from the false. We know how haughtily the Jews gloried in their father Abraham, and how presumptuously they boasted of the holiness of their descent; and yet there was scarcely one in a hundred among them who was not utterly degenerate and alienated from the faith of the Fathers. For this reason, Christ, in order to tear the mask from hypocrites, gives a short definition of a true Israelite, and, at the same time, removes the offense which would afterwards arise from the wicked obstinacy of the nation. For those who wished to be accounted the children of Abraham, and the holy people of God, were shortly afterwards to become the deadly enemies of the Gospel. That none may be discouraged or alarmed by the impiety which was generally found in almost all ranks, he gives a timely warning, that of those by whom the name of Israelites is assumed there are few who are true Israelites.
Again, as this passage contains a definition of Christianity, we must not pass by it slightly. To sum up the meaning of Christ in a few words, it ought to be observed that deceit is contrasted with uprightness and sincerity; (41) so that he calls those persons sly (42) and deceitful who are called in other parts of Scripture double in heart, (Psa_12:2.) Nor is it only that gross hypocrisy by which those who are conscious of their wickedness pretend to be good men, but likewise another inward hypocrisy, when men are so blinded by their vices that they not only deceive others but themselves. So then it is integrity of heart before God, and uprightness before men, that makes a Christian; but Christ points out chiefly that kind of deceit which is mentioned in Psa_32:2. In this passage
ἀληθῶς (truly) means something more than certainly. The Greek word, no doubt, is often used as a simple affirmation; but as we must here supply a contrast between the fact and the mere name, he is said to be truly, who is in reality what he is supposed to be.