As I noted yesterday, the call to faith comes immediately after the call to repentance. When one turns away from sin, one must immediately turn towards Christ, or else the evil spirit will return with seven other spirits and the results will be worse than ever (see Luke 11:24-26).
The word of God declares that whoever believes in Christ shall not perish but shall have eternal life (need I cite this? John 3:16). But what does it mean to believe? If such an astounding reward were to be granted for a simple assent to a few propositions of Christian doctrine, then people would be coming in droves to receive everlasting happiness. But I think that most people instinctively realize that believing in Christ means a lot more than offering an “OK, whatever,” to divine revelation. Therefore many refuse to come to Him.
When Jesus first said “Repent and believe,” He said: “believe in the Gospel” (Mark ). That is, believe in the good news of what He had come to reveal: the love of his Father, the Gift of the Holy Spirit, the hope of eternal life, the saving sacrifice that He would offer, the freedom and dignity—and hence the accountability—of the human person, and what is required if one is to live a life according to God’s will: in short, the Gospel is the mystery of faith.
To have Christian faith is not only to believe that God exists, that God is Trinitarian, that God became man in Jesus, that Jesus died for our sins and rose from the dead, etc—though all that is, of course, essential. To “believe in the Gospel” is also to live a life that expresses in practical ways what one has come to accept as the truth about God and man. Remember, St James said that faith without works is dead, and that even the demons believe in God, but they are still confined to Hell (-19). So it is not enough to say you believe in God (your faith has saved you!) and then live as if you didn’t. For in the end we will be judged not by what we professed, but by what we did—or didn’t do, as the case may be (see, for example, Matthew 25:31-46; 2Corinthians ; Revelation -13).
Faith does in fact save you—that is, faith properly understood. Saving faith is not merely saying something like the “sinner’s prayer” and accepting Jesus along with (what you think is) an impossible-to-lose salvation. Saving faith is an ongoing, living relationship with our Lord Jesus Christ, one that can either grow or die according to the free choices we make. God’s grace is always available, always offered, so nothing is lacking on his part. It is we who accept or reject his gift and hence accept or reject salvation. “Do not be deceived,” says the Apostle; “God is not mocked, for whatever a man sows, that he will also reap” (Galatians 6:7). In a sense (though perhaps unwittingly), those who say they believe—and who thus think they are irrevocably saved—yet who do not live the Gospel, are mocking God, who judges us not so much on what we say we believe, but on how we live it. To make a profession of faith is not to purchase an insurance policy, “the bearer of which shall be spared the pains of Hell at such a time as he or she departs this life.” No, God is personal and has created human persons in his image, and He expects us to enter into a personal relationship with Him, which, depending on our fidelity (his is guaranteed), will result in the saving or the losing of our souls.
That is why repentance (which must be ongoing, as our relationship with the Lord must also be) is required as a condition of faith. One who professes faith must no longer live as he used to (see Ephesians 4-5 and Colossians 3). Otherwise, what you call faith is not really faith, and you are not responding to the call of the Gospel.
So believe all that the Scriptures and the Church teach about God and his Son, that is, the content of the Gospel. Then “let your manner of life be worthy of the Gospel of Christ” (Philippians ). You will be saved by faith if—and only if—you put it into practice. One of Jesus’ favorite admonitions was: “Hear the word of God and keep it.”
I just discovered this text from Dietrich Bonhoeffer, and I thought it would be appropriate to append it to this post: "Are you worried because you find it so hard to believe? Don't be surprised at the difficulty of faith, if there is some part of your life where you are consciously resisting or disobeying the commandment of Jesus. Is there some part of your life which you are refusing to surrender at His behest, some sinful passion, maybe, or some animosity, some hope, perhaps your ambition or your reason? If so, you must not be surprised that you have not received the Holy Spirit, that prayer is difficult, or that your request for faith remains unanswered... The person who disobeys cannot believe. Only if you obey can you believe."