How can one experience Christ's redemption and salvation? The way is by faith. Paul said in Ephesians 2:8 and 9 that "you have been saved through faith, and this not of yourselves; it is the gift of God; not of works that no one should boast." Redemption and salvation are not something that we earn as merits. They do not originate from ourselves. They are not through the works that we do. There is nothing that a man can do to earn forgiveness or salvation. Both forgiveness of sins and salvation in life are by faith, and nothing else.
What is faith? Faith is first the seeing of what God has done to Christ on the cross. Hebrews 11:1 says that faith is the substantiation of things hoped for. Just as our eyes substantiate color and sights to us, so faith substantiates to us God's redemptive work accomplished two thousand years ago. When we see that God has judged Christ on our behalf, we are redeemed.
Faith is also a receiving of what Christ imparts to us. John 1:12 tells us that those who believe in Christ are those who receive Him. In other words, to believe is just to receive. Faith is not to believe in something that does not exist; rather, it is simply to receive something that is already there and given to you. If someone gives you a watch, all you need to do is to receive it. Once you receive it, the watch becomes yours. When God gives the saving life of Christ to us, all we need to do is to receive it. Once we receive this gift, it becomes ours forever. There is nothing we can do to add to what God has already done. We need only to receive it in faith. And there is nothing that can take away this gift once we have it; it is ours forever.
You may be very diligent to do good works. You may be very sincere in doing penance. But if you do not see Christ's accomplished work on the cross and do not receive His life in resurrection, you are still not saved. The Bible says at least one hundred fifty times that man is justified, saved, and receives eternal life through faith alone (Acts 16:31). In these one hundred fifty times, no other condition is attached. It is faith and nothing else.
Neither redemption nor salvation is through the works of man; both are works of God. Since they are works of God and since they are based on the righteousness of God and the life of Christ, they will never change. We can change, our mood can change, and our feelings can change, but God's righteous judgment will not change, nor will Christ's saving life change; they will stand forever. Even the heavens and the earth can change, but the righteous work of God and the saving life of Christ will never change. Christ's redemption and salvation are forever "insured." Once a person is saved, he is forever saved (John 10:28-29). Once you have received the gift of God, you will never lose it (Rom. 11:29). Once you become a child of God, you can never be lost again.