The Exclusivity of Saving Faith
“…that whoever believes in Him shall not perish, but have eternal life.” – John 3:16
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.
– John Calvin, Commentary on the Gospel of John, p. 125