Saint Paul speaks separately of confession with the mouth and of believing with the heart. He places oral confession first, and after it heartfelt faith. He does this in application to the passage cited above.
In the essence of the matter, everything is from faith in the heart. Out of the abundance of the heart the mouth speaks. Confession comes from faith planted in the heart.
Indeed, it is impossible without such faith. If it sometimes occurs without it, it has no significance in producing salvation.
But faith, when it is living and aflame, cannot remain hidden in the heart without showing itself. It comes forth of itself in word, in gaze, in movement, and in deeds.
Thus faith and its confession, in their truth, are inseparable. Here too the Apostle’s whole attention is directed to faith. When he added confession, he did not wish to indicate something separate, but the same faith.
The object of confession is the Lord Jesus: if you confess the Lord Jesus. This may be understood thus: if you confess the Lord Jesus as He is in truth, that is, the Son of God and God incarnate.
Or it may be taken directly: if you confess Jesus as Lord, that He is the Lord God. By this, confession of the divinity of Jesus Christ is established as a necessary condition of salvation.
The object of heartfelt faith is the Resurrection of Christ. Why so? Because belief began, and begins, with this. Upon this the whole subsequent structure of faith was and is founded.
That Jesus, called Christ, was crucified and died on the cross was evident to all and known to all. The apostolic preaching did not conceal this. On the contrary, it set it forth as its first point.
But it did not stop there. It always added: He died on the cross, but He also rose and lived (Rom 14:9). From this point faith began, and by it faith was conditioned.
For if He had only died, who would have begun to believe? The Apostles always portrayed faith in the Resurrection as the foundation of faith in Christ and of salvation (see 1 Cor 15:14).
From these objects it is also clear that the Apostle does not divide faith and confession. It is not as though one could confess the divinity of Jesus Christ without confessing His Resurrection.
Nor could one believe in His Resurrection without faith in His divinity, while doing no harm to the work of salvation. The two are indivisible.
That Jesus Christ is the Son of God and God is evident from His Resurrection, as the Apostle said at the beginning (see Rom 1:4). Faith in His Resurrection leads directly to confession of His divinity.
Therefore this passage, according to its meaning, may be read thus: if with your mouth you confess, and in your heart believe, that Jesus is Lord and that God raised Him from the dead, you will be saved.
The Apostle said, God raised Him, because of the weakness of the hearers. He did this so that the thought of how resurrection is possible would not enter in and cut off the course of faith.
By setting down, God raised Him, he removes every hesitation concerning possibility. For it is the common faith that all things are possible for God.
Chrysostom says: "That Christ is Lord is clear from the Resurrection, as the Apostle also said at the beginning of the Epistle: declared to be the Son of God by the Resurrection from the dead (cf. Rom 1:4). And that the Resurrection is not difficult has been proved even to the most ignorant by the power of Him Who raises."
That the One raised is also God, he has just said, when he commanded us to confess Jesus Christ as Lord. He Who is Lord is Himself able to rise.
If it is said that God raised Him, this is only to indicate His indivisibility from God the Father. For the Son of God, Who is God, became incarnate without leaving the bosom of the Father.
When He was raised by the Father, He Himself also participated in this action. Divine actions are indivisible. They proceed from the Tri-hypostatic Godhead.
The Resurrection of Christ is the work of God the Father, and of the Son, and of the Holy Spirit.
Thus, when you believe and confess in this way, that Jesus Christ is Lord, God incarnate, Who died and rose for our salvation, then you will be saved.
But how is this accomplished? The answer must be drawn from all that has gone before. It is an unalterable law that without fulfilling the commandments there is no salvation.
If you wish to enter into life, keep the commandments (cf. Mt 19:17), says the Lord. And again: not everyone who says to Me, Lord, Lord, shall enter the Kingdom of Heaven, but he who does the will of My Father Who is in heaven (cf. Mt 7:21).
Therefore, if salvation, which is entrance into the Kingdom and into life, is conditioned by confession and faith in Christ and in the Resurrection of Christ the Lord, it must be supposed that this is so because the fulfillment of the commandments is inseparably joined to them.
That is indeed the case. Let us recall what was said earlier about the nearness of the law. Saint Moses said: the law is near you, because it is written and lies before your eyes.
Though he added that it is also in the heart, this was only a promise. The Prophets later indicated its fulfillment in the future coming of the Promised One.
With Him, the whole law and all the commandments would be written not on parchment, but on the heart. This is exactly what happens.
The one who receives the Promised One Who has come cleaves to Him by faith. The one who cleaves to Him becomes one spirit with Him (see 1 Cor 6:17).
His Spirit is the sum of all the holy feelings, dispositions, and aspirations required by the commandments and constituting their fulfillment.
Therefore the one who cleaves by faith to Christ the Lord bears within himself the fulfillment of all the commandments. For that very reason he is saved.
One may come to the same conclusion by another path. He who believes and is baptized will be saved (cf. Mk 16:16), says the Lord. But whoever is baptized into Christ puts on Christ (see Gal 3:27).
Christ is everything holy and righteous. Therefore the one who believes in Christ bears within himself holiness and righteousness, which are the fulfillment of the commandments. Therefore he is saved.
Or again: the one baptized into the Lord is baptized into His death. This is so that, as Christ rose from the dead in the glory of the Father, he too may walk in newness of life.
Renewed life is a holy and righteous life, walking in all the commandments of God. Therefore, again, the believer is saved because he has the fulfillment of all the commandments.
Or thus: the one who believes and is baptized is reborn by the Holy Spirit unto new life. He becomes a child of God, not only in name but essentially.
This is because he is made Godlike, that is, holy, as his Begetter, the Tri-hypostatic God, is holy. In this he has salvation.
Thus, whatever one touches in faith in Christ the Lord, from everything one comes to one conclusion. The one who truly believes is saved.
But this is because, according to the ordering of faith, he becomes a fulfiller of all the commandments. He bears them inscribed in the heart, in holy feelings and dispositions, created there by the Holy Spirit.