There are many instances of the occurrence of this metaphor in the New Testament, but none is exactly like this. We read, for example, of 'a great door and effectual' being opened to Paul for the free ministry of the word; and to the angel of the Church in Philadelphia, 'He that openeth and none shall shut' graciously says, 'I have set before thee a door opened, which none can shut.' But here the door is faith, that is to say faith is conceived of as the means of entrance for the Gentiles into the Kingdom, which, till then, Jews had supposed to be entered by hereditary rite.
I. Faith is the means of our entrance into the Kingdom.
The Jew thought that birth and the rite of circumcision were the door, but the 'rehearsing' of the experiences of Paul and Barnabas on their first missionary tour shattered that notion by the logic of facts. Instead of that narrow postern another doorway had been broken in the wall of the heavenly city, and it was wide enough to admit of multitudes entering. Gentiles had plainly come in. How had they come in? By believing in Jesus. Whatever became of previous exclusive theories, there was a fact that had to be taken into account. It distinctly proved that faith was 'the gate of the Lord into which,' not the circumcised but the 'righteous,' who were righteous because believing, 'should enter.'
We must not forget the other use of the metaphor, by our Lord Himself, in which. He declares that He is the Door. The two representations are varying but entirely harmonious, for the one refers to the objective fact of Christ's work as making it possible that we should draw near to and dwell with God, and the other to our subjective appropriation of that possibility, and making it a reality in our own blessed experience.
II. Faith is the means of God's entrance into our hearts.
We possess the mysterious and awful power of shutting God out of these hearts. And faith, which in one aspect is our means of entrance into the Kingdom of God, is, in another, the means of God's entrance into us. The Psalm, which invokes the divine presence in the Temple, calls on the 'everlasting doors' to be 'lifted up,' and promises that then 'the King of Glory will come in.' And the voice of the ascended Christ, the King of Glory, knocking at the closed door, calls on us with our own hands to open the door, and promises that He 'will come in.'
Paul prayed for the Ephesian Christians 'that Christ may dwell in your hearts through faith,' and there is no other way by which His indwelling is possible. Faith is not constituted the condition of that divine indwelling by any arbitrary appointment, as a sovereign might determine that he would enter a city by a certain route, chosen without any special reason from amongst many, but in the nature of things it is necessary that trust, and love which follows trust, and longing which follows love should be active in a soul if Christ is to enter in and abide there.
III. Faith is the means of the entrance of the Kingdom into us.
If Christ comes in He comes with His pierced hands full of gifts. Through our faith we receive all spiritual blessings. But we must ever remember, what this metaphor most forcibly sets forth, that faith is but the means of entrance. It has no worth in itself, but is precious only because it admits the true wealth. The door is nothing. It is only an opening. Faith is the pipe that brings the water, the flinging wide the shutters that the light may flood the dark room, the putting oneself into the path of the electric circuit. Salvation is not arbitrarily connected with faith. It is not the reward of faith but the possession of what comes through faith, and cannot come in any other way. Our 'hearts' are 'purified by faith,' because faith admits into our hearts the life, and instals as dominant in them the powers, the motives, the Spirit, which purify. We are 'saved by faith,' for faith brings into our spirits the Christ who saves His people from their sins, when He abides in them and they abide in Him through their faith.