It would be something of an understatement to say that Matthew 16.19 has been a crux interpretum:
19 δώσω σοι τὰς κλεῖδας τῆς βασιλείας τῶν οὐρανῶν, καὶ ὃ ἐὰν δήσῃς ἐπὶ τῆς γῆς ἔσται δεδεμένον ἐν τοῖς οὐρανοῖς, καὶ ὃ ἐὰν λύσῃς ἐπὶ τῆς γῆς ἔσται λελυμένον ἐν τοῖς οὐρανοῖς.
“I will give to you the keys of the kingdom of the heavens, and whatever you bind on earth will have been bound in the heavens, and whatever you loose on earth will have been loosed in the heavens.”
What is the nature of the “keys”? How do they relate to discipline? Authority? Power?
If we compare Christ’s statement here with other dominical sayings elsewhere in the Gospels, I believe that we can better establish his meaning in this passage, and that that meaning has to do primarily with teaching; more closely, “the keys” are the preaching of the Gospel, by which heaven is opened when it is received by faith, and shut when it is obstinately rejected.
We turn first to one of Jesus’ woes pronounced against the scribes and Pharisees, where a similar metaphor of the door or entryway is used. Jesus says:
13 Οὐαὶ δὲ ὑμῖν, γραμματεῖς καὶ Φαρισαῖοι ὑποκριταί, ὅτι κλείετε τὴν βασιλείαν τῶν οὐρανῶν ἔμπροσθεν τῶν ἀνθρώπων· ὑμεῖς γὰρ οὐκ εἰσέρχεσθε, οὐδὲ τοὺς εἰσερχομένους ἀφίετε εἰσελθεῖν.
“And woe to you, scribes and Pharisees, hypocrites, since you shut the kingdom of the heavens in front of men; for you yourselves do not go in, and you prevent those going in from entering.”
As the context makes clear, Jesus rebukes the scribes and Pharisees chiefly for abusing the teaching office that has been entrusted to them. They “sit in Moses’ seat,” but teach and live in such a way that they are guilty of gross hypocrisy. Thus Jesus more than once refers to them as “blind guides.” In so far as they teach what is in accord with Moses, they are to be obeyed; but when they do not, they are to be rejected. All instruction must be in submission to the one who is, in one sense, the only instructor, Christ himself (23.10). When teachers pervert the pure Word of God, as the scribes and Pharisees were doing, they effectively shut the heavenly kingdom against those who would enter. Their keys have been misused.
This interpretation is confirmed and made perhaps even more explicit by the parallel passage in Luke 11, where we find both a “key” and a reference to “knowledge.”
52 οὐαὶ ὑμῖν τοῖς νομικοῖς, ὅτι ἤρατε τὴν κλεῖδα τῆς γνώσεως· αὐτοὶ οὐκ εἰσήλθατε καὶ τοὺς εἰσερχομένους ἐκωλύσατε.
“Woe to you, lawyers! For you have taken away the key of knowledge. You yourselves did not enter and you hindered those entering.”
Again, the lawyers are charged with wickedness because they have misunderstood and misappropriated the Word of God, and by so doing they have become a stumbling-block to those who would come into the kingdom. As Calvin comments on this passage, “We know how powerfully a foolish reverence for false teachers hinders people from getting clear of their erroneous views.” He continues shortly thereafter: “[S]ince the government of the Church was in their hands, they ought to have been, as it were, porters for the kingdom of heaven.” The lawyers have “taken away the key of knowledge,” Calvin says, because, “though they were the guardians of the Law of God, they deprived the people of the true understanding of it.”
This deprivation keeps men from heaven, because all are sold under sin, and it is only the “holy doctrine” of the Word of God that “open[s] heaven to us.” Taught aright, this Word “admit[s] believers into eternal life, and exclude[s] unbelievers from all expectation of it.” Thus the Word is the key to the kingdom of heaven. Calvin comments: “Now the doctrine of religion may be said to be the door by which we enter into life, and therefore Scripture says metaphorically, that the keys of the kingdom of heaven are given to pastors, as I have explained more fully under Matthew 16:19.”
When we turn to that passage of the commentary, we a fuller exposition of the basic point: at the essential core, it is the Word of the Gospel, as the apogee of the revelatory Word of God in Scripture, that binds and looses.
The comparison of the keys is very properly applied to the office of teaching; as when Christ says (Luke 11:52) that the scribes and Pharisees, in like manner, have the key of the kingdom of heaven, because they are expounders of the law. We know that there is no other way in which the gate of life is opened to us than by the word of God; and hence it follows that the key is placed, as it were, in the hands of the ministers of the word.[…]
The second metaphor, or comparison, is intended directly to point out the forgiveness of sins; for Christ, in delivering us, by his Gospel, from the condemnation of eternal death, looses the cords of the curse by which we are held bound. The doctrine of the Gospel is, therefore, declared to be appointed for loosing our bonds, that, being loosed on earth by the voice and testimony of men, we may be actually loosed in heaven. But as there are many who not only are guilty of wickedly rejecting the deliverance that is offered to them, but by their obstinacy bring down on themselves a heavier judgment, the power and authority to bind is likewise granted to the ministers of the Gospel. It must be observed, however, that this does not belong to the nature of the Gospel, but is accidental….[…]
The substance of this statement is, that Christ intended to assure his followers of the salvation promised to them in the Gospel, that they might expect it as firmly as if he were himself to descend from heaven to bear testimony concerning it; and, on the other hand, to strike despisers with terror, that they might not expect their mockery of the ministers of the word to remain unpunished. Both are exceedingly necessary; for the inestimable treasure of life is exhibited to us in earthen vessels, (2 Corinthians 4:7,) and had not the authority of the doctrine been established in this manner, the faith of it would have been, almost every moment, ready to give way. The reason why the ungodly become so daring and presumptuous is, that they imagine they have to deal with men. Christ therefore declares that, by the preaching of the Gospel, is revealed on the earth what will be the heavenly judgment of God, and that the certainty of life or death is not to be obtained from any other source.
If this reading is correct, then the key to the keys (as it were) is the faithful proclamation of the Gospel of Jesus Christ, and the reading of Matthew 16 in conjunction with Matthew 23 and Luke 11, by way of the analogia Scripturae, can go some way toward clearing the difficulties that vex the interpretation of some very contested verses. What is the power of the keys? Simply put, it is the Gospel; “for it is the power of God for salvation to everyone who believes, to the Jew first and also to the Greek.” Why? Because the Word of the Gospel tells us about Jesus, the Word made flesh, and he himself is “the holy one, the true one, who has the key of David, who opens and no one will shut, who shuts and no one opens.”