Hebrews 8:10

10For this is the covenant that I will make, etc. There are two main parts in this covenant; the first regards the gratuitous remission of sins; and the other, the inward renovation of the heart; there is a third which depends on the second, and that is the illumination of the mind as to the knowledge of God. There are here many things most deserving of notice.

The first is, that God calls us to himself without effect as long as he speaks to us in no other way than by the voice of man. He indeed teaches us and commands what is right but he speaks to the deaf; for when we seem to hear anything, our ears are only struck by an empty sound; and the heart, full of depravity and perverseness, rejects every wholesome doctrine. In short, the word of God never penetrates into our hearts, for they are iron and stone until they are softened by him; nay, they have engraven on them a contrary law, for perverse passions rule within, which lead us to rebellion. In vain then does God proclaim his Law by the voice of man, unless he writes it by his Spirit on our hearts, that is, unless he forms and prepares us for obedience. It hence appears of what avail is freewill and the uprightness of nature before God regenerates us. We will indeed and choose freely; but our will is carried away by a sort of insane impulse to resist God. Thus it comes that the Law is ruinous and fatal to us as long as it remains written only on tables of stone, as Paul also teaches us. (2 Corinthians 3:3.) In short, we then only obediently embrace what God commands, when by his Spirit he changes and corrects the natural pravity of our hearts; otherwise he finds nothing in us but corrupt affections and a heart wholly given up to evil. The declaration indeed is clear, that a new covenant is made according to which God engraves his laws on our hearts, for otherwise it would be in vain and of no effect. (134)

The second particular refers to the gratuitous pardon of sins. Though they have sinned, saith the Lord, yet I will pardon them. This part is also most necessary; for God never so forms us for obedience to his righteousness, but that many corrupt affections of the flesh still remain; nay, it is only in part that the viciousness of our nature is corrected; so that evil lusts break out now and then. And hence is that contest of which Paul complains, when the godly do not obey God as they ought, but in various ways offend. (Romans 7:13.) Whatever desire then there may be in us to live righteously, we are still guilty of eternal death before God, because our life is ever very far from the perfection which the Law requires. There would then be no stability in the covenant, except God gratuitously forgave our sins. But it is the peculiar privilege of the faithful who have once embraced the covenant offered to them in Christ, that they feel assured that God is propitious to them; nor is the sin to which they are liable, a hindrance to them, for they have the promise of pardon.

And it must be observed that this pardon is promised to them, not for one day only, but to the very end of life, so that they have a daily reconciliation with God. For this favor is extended to the whole of Christ’s kingdom, as Paul abundantly proves in the fifth chapter of his second Epistle to the Corinthians. And doubtless this is the only true asylum of our faith, to which if we flee not, constant despair must be our lot. For we are all of us guilty; nor can we be otherwise released then by fleeing to God’s mercy, which alone can pardon us.

And they shall be to me, etc. It is the fruit of the covenant, that God chooses us for his people, and assures us that he will be the guardian of our salvation. This is indeed the meaning of these words, And I will be to them a God; for he is not the God of the dead, nor does he take us under his protection, but that he may make us partakers of righteousness and of life, so that David justly exclaims, “Blessed are the people to whom the Lord is God (Psalms 144:15.) There is further no doubt but that this truth belongs also to us; for though the Israelites had the first place, and are the proper and legitimate heirs of the covenant, yet their prerogative does not hinder us from having also a title to it. In short, however far and wide the kingdom of Christ extends, this covenant of salvation is of the same extent.

But it may be asked, whether there was under the Law a sure and certain promise of salvation, whether the fathers had the gift of the Spirit, whether they enjoyed God’s paternal favor through the remission of sins? Yes, it is evident that they worshipped God with a sincere heart and a pure conscience, and that they walked in his commandments, and this could not have been the case except they had been inwardly taught by the Spirit; and it is also evident, that whenever they thought of their sins, they were raised up by the assurance of a gratuitous pardon. And yet the Apostle, by referring the prophecy of Jeremiah to the coming of Christ, seems to rob them of these blessings. To this I reply, that he does not expressly deny that God formerly wrote his Law on their hearts and pardoned their sins, but he makes a comparison between the less and the greater. As then the Father has put forth more fully the power of his Spirit under the kingdom of Christ, and has poured forth more abundantly his mercy on mankind, this exuberance renders insignificant the small portion of grace which he had been pleased to bestow on the fathers. We also see that the promises were then obscure and intricate, so that they shone only like the moon and stars in comparison with the clear light of the Gospel which shines brightly on us.

If it be objected and said, that the faith and obedience of Abraham so excelled, that hardly any such an example can at this day be found in the whole world; my answer is this, that the question here is not about persons, but that reference is made to the economical condition of the Church. Besides, whatever spiritual gifts the fathers obtained, they were accidental as it were to their age; for it was necessary for them to direct their eyes to Christ in order to become possessed of them. Hence it was not without reason that the Apostle, in comparing the Gospel with the Law, took away from the latter what is peculiar to the former. There is yet no reason why God should not have extended the grace of the new covenant to the fathers. This is the true solution of the question.