16. For God so loved the world. Christ opens up the first cause, and, as it were, the source of our salvation, and he does so, that no doubt may remain; for our minds cannot find calm repose, until we arrive at the unmerited love of God. As the whole matter of our salvation must not be sought any where else than in Christ, so we must see whence Christ came to us, and why he was offered to be our Savior. Both points are distinctly stated to us: namely, that faith in Christ brings life to all, and that Christ brought life, because the Heavenly Father loves the human race, and wishes that they should not perish. And this order ought to be carefully observed; for such is the wicked ambition which belongs to our nature, that when the question relates to the origin of our salvation, we quickly form diabolical imaginations about our own merits. Accordingly, we imagine that God is reconciled to us, because he has reckoned us worthy that he should look upon us. But Scripture everywhere extols his pure and unmingled mercy, which sets aside all merits.
And the words of Christ mean nothing else, when he declares the cause to be in the love of God. For if we wish to ascend higher, the Spirit shuts the door by the mouth of Paul, when he informs us that this love was founded on the purpose of his will, (Ephesians 1:5.) And, indeed, it is very evident that Christ spoke in this manner, in order to draw away men from the contemplation of themselves to look at the mercy of God alone. Nor does he say that God was moved to deliver us, because he perceived in us something that was worthy of so excellent a blessing, but ascribes the glory of our deliverance entirely to his love. And this is still more clear from what follows; for he adds, that God gave his Son to men, that they may not perish. Hence it follows that, until Christ bestow his aid in rescuing the lost, all are destined to eternal destruction. This is also demonstrated by Paul from a consideration of the time;
for he loved us while we were still enemies by sin, (Romans 5:8, 10.)
And, indeed, where sin reigns, we shall find nothing but the wrath of God, which draws death along with it. It is mercy, therefore, that reconciles us to God, that he may likewise restore us to life.
This mode of expression, however, may appear to be at variance with many passages of Scripture, which lay in Christ the first foundation of the love of God to us, and show that out of him we are hated by God. But we ought to remember — what I have already stated — that the secret love with which the Heavenly Father loved us in himself is higher than all other causes; but that the grace which he wishes to be made known to us, and by which we are excited to the hope of salvation, commences with the reconciliation which was procured through Christ. For since he necessarily hates sin, how shall we believe that we are loved by him, until atonement has been made for those sins on account of which he is justly offended at us? Thus, the love of Christ must intervene for the purpose of reconciling God to us, before we have any experience of his fatherly kindness. But as we are first informed that God, because he loved us, gave his Son to die for us, so it is immediately added, that it is Christ alone on whom, strictly speaking, faith ought to look.
He gave his only-begotten Son, that whosoever believeth on him may not perish. This, he says, is the proper look of faith, to be fixed on Christ, in whom it beholds the breast of God filled with love: this is a firm and enduring support, to rely on the death of Christ as the only pledge of that love. The word only-begotten is emphatic, (ἐμφατικὸ ν) to magnify the fervor of the love of God towards us. For as men are not easily convinced that God loves them, in order to remove all doubt, he has expressly stated that we are so very dear to God that, on our account, he did not even spare his only-begotten Son. Since, therefore, God has most abundantly testified his love towards us, whoever is not satisfied with this testimony, and still remains in doubt, offers a high insult to Christ, as if he had been an ordinary man given up at random to death. But we ought rather to consider that, in proportion to the estimation in which God holds his only-begotten Son, so much the more precious did our salvation appear to him, for the ransom of which he chose that his only-begotten Son should die. To this name Christ has a right, because he is by nature the only Son of God; and he communicates this honor to us by adoption, when we are engrafted into his body.
That whosoever believeth on him may not perish. It is a remarkable commendation of faith, that it frees us from everlasting destruction. For he intended expressly to state that, though we appear to have been born to death, undoubted deliverance is offered to us by the faith of Christ; and, therefore, that we ought not to fear death, which otherwise hangs over us. And he has employed the universal term whosoever, both to invite all indiscriminately to partake of life, and to cut off every excuse from unbelievers. Such is also the import of the term World, which he formerly used; for though nothing will be found in the world that is worthy of the favor of God, yet he shows himself to be reconciled to the whole world, when he invites all men without exception to the faith of Christ, which is nothing else than an entrance into life.
Let us remember, on the other hand, that while life is promised universally to all who believe in Christ, still faith is not common to all. For Christ is made known and held out to the view of all, but the elect alone are they whose eyes God opens, that they may seek him by faith. Here, too, is displayed a wonderful effect of faith; for by it we receive Christ such as he is given to us by the Father — that is, as having freed us from the condemnation of eternal death, and made us heirs of eternal life, because, by the sacrifice of his death, he has atoned for our sins, that nothing may prevent God from acknowledging us as his sons. Since, therefore, faith embraces Christ, with the efficacy of his death and the fruit of his resurrection, we need not wonder if by it we obtain likewise the life of Christ.
Still it is not yet very evident why and how faith bestows life upon us. Is it because Christ renews us by his Spirit, that the righteousness of God may live and be vigorous in us; or is it because, having been cleansed by his blood, we are accounted righteous before God by a free pardon? It is indeed certain, that these two things are always joined together; but as the certainty of salvation is the subject now in hand, we ought chiefly to hold by this reason, that we live, because God loves us freely by not imputing to us our sins. For this reason sacrifice is expressly mentioned, by which, together with sins, the curse and death are destroyed. I have already explained the object of these two clauses,
which is, to inform us that in Christ we regain the possession of life, of which we are destitute in ourselves; for in this wretched condition of mankind, redemption, in the order of time, goes before salvation.
17. For God sent not his Son into the world to condemn the world. It is a confirmation of the preceding statement; for it was not in vain that God sent his own Son to us. He came not to destroy; and therefore it follows, that it is the peculiar office of the Son of God, that all who believe may obtain salvation by him. There is now no reason why any man should be in a state of hesitation, or of distressing anxiety, as to the manner in which he may escape death, when we believe that it was the purpose of God that Christ should deliver us from it. The word world is again repeated, that no man may think himself wholly excluded, if he only keep the road of faith.
The word judge (πρίνω) is here put for condemn, as in many other passages. When he declares that he did not come to condemn the world, he thus points out the actual design of his coming; for what need was there that Christ should come to destroy us who were utterly ruined? We ought not, therefore, to look at any thing else in Christ, than that God, out of his boundless goodness chose to extend his aid for saving us who were lost; and whenever our sins press us — whenever Satan would drive us to despair — we ought to hold out this shield, that God is unwilling that we should be overwhelmed with everlasting destruction, because he has appointed his Son to be the salvation of the world.
When Christ says, in other passages, that he is come to judgment, (John 9:39;) when he is called a stone of offense, (1 Peter 2:7;) when he is said to be set for the destruction of many, (Luke 2:34:) this may be regarded as accidental, or as arising from a different cause; for they who reject the grace offered in him deserve to find him the Judge and Avenger of contempt so unworthy and base. A striking instance of this may be seen in the Gospel; for though it is strictly
the power of God for salvation to every one who believeth, (Romans 1:16,)
the ingratitude of many causes it to become to them death.. Both have been well expressed by Paul, when he boasts of
having vengeance at hand, by which he will punish all the adversaries of his doctrine after that the obedience of the godly shall have been fulfilled, (2 Corinthians 10:6)
The meaning amounts to this, that the Gospel is especially, and in the first instance, appointed for believers, that it may be salvation to them; but that afterwards believers will not escape unpunished who, despising the grace of Christ, chose to have him as the Author of death rather than of life.
 John Calvin, Calvin’s Commentaries: John, Jn 3:16–17.