Repentance and faith
Now after that John was put in prison, Jesus came into Galilee, preaching the gospel of the kingdom of God, and saying, The time is fulfilled, and the kingdom of God is at hand: repent ye, and believe the gospel. Mark 1:14-15
From the very beginning, the Christian message, the gospel, has insisted upon these two things: repentance and faith. Many years later, the apostle Paul would characterize his own ministry in much the same way: "I kept back nothing that was profitable unto you," he said, "but have shewed you, and have taught you publicly, and from house to house, testifying both to the Jews, and also to the Greeks, repentance toward God, and faith toward our Lord Jesus Christ" (Acts 20:21).
And yet, what is the significance of this? Why call men and women to repent of their sins and to faith in Christ? What was Jesus and his apostles aiming at? Well, the New Testament is replete with explanation. For example, in the book of Acts we are told that it is so that the sins of those who repent and believe might be blotted out: "Repent ye therefore, and be converted, that your sins may be blotted out" (Acts 3:19). It is so that they might receive the forgiveness of sins and justification before God: "Be it known unto you therefore, men and brethren, that through this man [Jesus Christ] is preached unto you the forgiveness of sins: and by him all that believe are justified from all things, from which ye could not be justified by the law of Moses" (Acts 13:38-39). It is so that they might be recovered from the power of darkness and Satan, receive the forgiveness of sins and an inheritance among those who are thus sanctified: "To open their eyes, and to turn them from darkness to light, and from the power of Satan unto God, that they may receive forgiveness of sins, and inheritance among them which are sanctified by faith that is in me" (Acts 26:18). We could multiply references like this throughout the New Testament.
Of course, both repentance (Acts 11:18; 2 Tim. 2:25) and faith (Eph. 2:8; Phil. 1:29) are gifts of God. But we must not think that because God must initiate conversion that therefore it matters not whether or not we repent of our sins and believe the gospel. No, if we would be justified, forgiven, and sanctified, we must repent and believe. There is no other way.
Why would God do this? Why insist upon repentance and faith? Repentance is insisted upon because salvation from sin is simply incompatible with salvation in sin. If we would be saved, we must turn from our sins. Jesus is not only Savior, but he is Lord, and you cannot have him as the former unless you submit to him as the latter. On the other hand, faith is insisted upon because God will be seen to be glorious. Faith is the eye by which we look away from ourselves and our self-righteousness to Christ and his righteousness (cf. Isa. 45:22). Faith is the hand by which we receive the water of life. It is not in itself meritorious in any sense, does not contribute from its own store toward our salvation, but finds, sees, and receives it complete and whole in Jesus Christ alone.
In other words, God requires faith and repentance because he is good to us. It is for our good that we turn from sins which are inherently self-destructive and blind us to the glory of God. And it is for our good that we see and savor the love and kindness and righteousness and salvation which can only be found in our Lord and Savior Jesus Christ. Thanks be unto God for his inexpressible gift!