This is another very good question. And as always, what matters is not what men say about this, but what God says about the issue. So with that in mind, let us direct our attention to what the Scripture says.
The first thing that must be established is that there is nothing we can do to earn our way into heaven. Ephesians 2:8-9 quite clearly states that God’s grace saves us, through faith. Forgiveness, the apostle Paul says, is a gift from God, not something that any of us can earn. He corroborates this in Romans 3:23-25:
“…for all have sinned, and fall short of the glory of God, and are justified by His grace as a gift, through the redemption that is in Christ Jesus, whom God put forward as a propitiation by His blood, to be received by faith. This was to show God’s righteousness, because in His divine forbearance He had passed over former sins.”
These two passages clearly show us that the grace of God is what saves us from sins, when the blood of Christ is applied to our souls (blood has always been an agent of purification, for more, read through Exodus, Leviticus, and Hebrews). These Scriptures also tell us that the blood of Christ becomes active upon our souls through faith. Faith, according to Scripture, is a prerequisite of God’s grace. This is not something new in the teachings of Christ and His apostles. This has always been the case. Hebrews 11:6 tells us that it is impossible to please God without faith. Therefore we must ask the next question: what is faith?
To answer this question, we could simply turn to Hebrews 11:1, which gives us a good definition, but we must also then read the rest of the chapter. This text is a treatise on how faith manifests itself in the lives of men. In each and every case, from Abel in verse 4, to the many unnamed righteous in verses 33-38, we are not told what faith is, but shown. In each and every case, faith motivates these men (and women) to obey the commandments of God. These texts are in complete harmony with what is written in James 2:14-26:
“What good is it, my brothers, if someone says he has faith but does not have works [of obedience]? Can that faith save him? If a brother or sister is poorly clothed and lacking in daily food, and one of you says to them, “Go in peace, be warmed and filled,” without giving them the things needed for the body, what good is that? So also faith by itself, if it does not have works, is dead. But someone will say, “You have faith, and I have works.” Show me your faith apart from your works, and I will show you my faith by my works. You believe that God is one; you do well. Even the demons believe–and shudder! Do you want to be shown, you foolish person, that faith apart from works is useless? Was not Abraham our father justified by works when he offered up his son Isaac on the altar? You see that faith was active along with his works, and faith was completed by his works; and the Scripture was fulfilled that says, ‘Abraham believed God and it was counted to him as righteousness’–and he was called a friend of God. You see that a person is justified by works and not by faith alone. And in the same way was not also Rahab the prostitute justified by works when she received the messengers and sent them out by another way? For as the body apart from the spirit is dead, so also faith apart from works is dead.”
So from what Scripture tells us so far, God’s grace is what saves us, when he applies the purifying blood of Christ to our souls, but that true faith is properly defined as “belief-based obedience,” and that works are indeed not what saves us, but a prerequisite of God’s grace becoming active in our lives. So now that we have observed this from the Scriptures, we must then ask the final question: when is Christ’s blood applied to my sins?
In order to answer this question, we must also ask another: to whom were these men writing? In each case, the answer is this: to other Christians. Therefore, we can use our common sense to conclude that the blood of Christ is applied to us when we make the decision to become a disciple of Christ. So, we must ask yet another question: how do I become a Christian? As always, let us direct our attention to what the Scripture says. There are a number of passages we can go to for the answer to this question, but I happen to like Romans 6:3-4 the best:
“Do you not know that all of us who have been baptized into Christ Jesus were baptized into is death? We were buried therefore with Him by baptism into death, in order that, just as Christ was raised from the dead by the glory of the father, so we too might walk in newness of life.”
The apostle Paul goes on to say in the following verses that this death is a death to sin. It should no longer have a hold over us. We will continue to sin every now and then, yes, but it should no longer be a regular practice in our lives. Also, this death to sin is a death to the consequences of sin, which Romans 6:23 says is death, or eternal separation from God, which is the “second death” referred to in the book of Revelation. This death to sin, and our spiritual resurrection, or “rebirth,” if you will (John 3:3), occurs when we are baptized. The apostle Paul here is giving the theology behind the commandments found in Matthew 28:18-20, Mark 16:15-16, and Acts 2:38, just to name a few other passages.
In Romans 6:5-14, Paul tells us that we must continue to live in obedience to the will of God, and continue our struggle against sin, which he describes as warfare in Ephesians 6:10-20, in which he gives us the tools we can use in this spiritual form of combat.
So, now that we have read what New Testament Scripture says regarding this issue, let us consider a final answer to your question, “How do we obtain salvation?”
Salvation, therefore, is a gift from God, which is applied through the blood of Christ, when we dedicate our lives to His service by being immersed in water (Acts 8:26-40; Romans 6:4 “buried”), an act of faith. He continues to apply the blood of Christ to forgive our sins if we keep walking by faith (belief-based obedience to His commands).