Matthew 16:18

18.And I say to thee. By these words Christ declares how highly he is delighted with the confession of Peter, since he bestows upon it so large a reward. For, though he had already given to his disciple, Simon, the name of Peter, (Matthew 10:2; John 1:42,) and had, out of his undeserved goodness, appointed him to be an apostle, yet these gifts, though freely bestowed, (439) are here ascribed to faith as if they had been a reward, which we not unfrequently find in Scripture. Peter receives a twofold honor, the former part of which relates to his personal advantage, and the latter to his office as an Apostle.

Thou art Peter. By these words our Lord assures him that it was not without a good reason that he had formerly given him this name, because, as a living stone (1 Peter 2:5) in the temple of God, he retains his stedfastness. This extends, no doubt, to all believers, each of whom is a temple of God, (1 Corinthians 6:19,) and who, united to each other by faith, make together one temple, (Ephesians 2:21.) But it denotes also the distinguished excellence of Peter above the rest, as each in his own order receives more or less, according to the measure of the gift of Christ, (Ephesians 4:7.)

And on this rock. Hence it is evident how the name Peter comes to be applied both to Simon individually, and to other believers. It is because they are founded on the faith of Christ, and joined together, by a holy consent, into a spiritual building, that God may dwell in the midst of them, (Ezekiel 43:7.) For Christ, by announcing that this would be the common foundation of the whole Church, intended to associate with Peter all the godly that would ever exist in the world. “You are now,” said he, “a very small number of men, and therefore the confession which you have now made is not at present supposed to have much weight; but ere long a time will arrive when that confession shall assume a lofty character, and shall be much more widely spread.” And this was eminently fitted to excite his disciples to perseverance, that though their faith was little known and little esteemed, yet they had been chosen by the Lord as the first-fruits, that out of this mean commencement there might arise a new Church, which would prove victorious against all the machinations of hell.

Shall not prevail against it. The pronoun it ( αὐτὢς) may refer either to faith or to the Church; but the latter meaning is more appropriate. Against all the power of Satan the firmness of the Church will prove to be invincible, because the truth of God, on which the faith of the Church rests, will ever remain unshaken. And to this statement corresponds that saying of John,

This is the victory which overcometh the world, your faith,
(1 John 5:4.)

It is a promise which eminently deserves our observation, that all who are united to Christ, and acknowledge him to be Christ and Mediator, will remain to the end safe from all danger; for what is said of the body of the Church belongs to each of its members, since they are one in Christ. Yet this passage also instructs us, that so long as the Church shall continue to be a pilgrim on the earth, she will never enjoy rest, but will be exposed to many attacks; for, when it is declared that Satan will not conquer, this implies that he will be her constant enemy. While, therefore, we rely on this promise of Christ, feel ourselves at liberty to boast against Satan, and already triumph by faith over all his forces; let us learn, on the other hand, that this promise is, as it were, the sound of a trumpet, calling us to be always ready and prepared for battle. By the word gates ( πύλαι) is unquestionably meant every kind of power and of weapons of war.