A Believer Can Not Turn His Back on the Lord
First and foremost, it's important for us to understand how we become a Christian, that is, how we are saved. To summarize from Scripture, the Bible teaches we are saved by God's grace, not our own will or works. Our salvation is not contingent on what we do before or even after we have been saved because we are counted righteous from the moment because of what Jesus did.
Moreover, all of our sins have been forgiven by Christ's death and resurrection: past, present and future. In a spiritual sense, we have already been "perfected" (Hebrews 10:14) by our faith in that God placed our sin on Christ on the cross and made us spiritually new, once again because of Christ's obedience. Christ took our penalty for sin and we were assigned His righteousness by our faith.
So if a person has truly received God's gracious gift of faith, then that person will go to heaven upon death regardless of how many sins the person may have committed. His or her actions or works did not after becoming a believer do not determine his salvation because, as we've shown, salvation is totally due to actions taken on God's part, not man's. Clearly, this means that a believer cannot lose or forfeit salvation. Ephesians 2:8 says that salvation is a gift of God, and Romans 11:29 says "the gifts and the calling of God are irrevocable." Therefore, if God has saved us, we are saved forevermore.
Scripture gives us examples of believers who sinned in major ways yet remained in God's family. Consider the following:
1. Peter denied he even knew Christ (Luke 22:55-62), but Jesus later restored and forgave Peter, demonstrating that Peter still belonged to Jesus despite his grievous sin. 2. Ananias and Sapphira were believers who sinned and were judged on earth but remained saved eternally (Acts 5:1-10). Peter said to Ananias in Acts 5:3-4 that he lied not only to men but also to the Holy Spirit, Who Peter said was dwelling in Ananias' heart. This was proof of his salvation and righteousness by faith (Romans 8:9-10), yet Ananias was judged sternly by God (on earth) for his sin. 3. The unnamed believer in 1 Corinthians 5:1-5 was punished temporally (again, on earth) yet was still saved and his spirit welcomed into God's presence, as Paul affirmed in v.5.
These examples prove that our sin does not separate us from God, as Paul says in Romans 8. Nevertheless, our actions as Christians do have other consequences, both here and in eternity. As the examples above attest, God requires that we discipline those in the church who continue in a life of sin. Matthew 18:15-20 gives clear instructions as to how sinning believers are to be handled. Ultimately, if they refuse to stop sinning, we are to put them out of the church. This is for the destruction of their flesh, not that they would lose their salvation (see 1 Cor. 5:1-5), with the ultimate goal of restoring them to fellowship (as Jesus did with Peter).
The Lord makes clear that He will discipline those He loves. Therefore, if we continue in sin, we can expect to be put out of fellowship with the church, as well as God's chastisement. Hebrews 12:4-7 makes this clear:
You have not yet resisted to the point of shedding blood in your striving against sin; and you have forgotten the exhortation which is addressed to you as sons, "MY SON, DO NOT REGARD LIGHTLY THE DISCIPLINE OF THE LORD, NOR FAINT WHEN YOU ARE REPROVED BY HIM; FOR THOSE WHOM THE LORD LOVES HE DISCIPLINES, AND HE SCOURGES EVERY SON WHOM HE RECEIVES." It is for discipline that you endure; God deals with you as with sons; for what son is there whom his father does not discipline?
We also face consequences in heaven for what we do here on earth as believers. Again, our salvation is not in question, but the level of rewards we will receive in heaven depends on how we serve God while on earth. This is made most clear in 1 Corinthians 3:9-17:
For we are God's fellow workers; you are God's field, God's building. According to the grace of God which was given to me, like a wise master builder I laid a foundation, and another is building on it. But each man must be careful how he builds on it. For no man can lay a foundation other than the one which is laid, which is Jesus Christ. Now if any man builds on the foundation with gold, silver, precious stones, wood, hay, straw, each man's work will become evident; for the day will show it because it is to be revealed with fire, and the fire itself will test the quality of each man's work. If any man's work which he has built on it remains, he will receive a reward. If any man's work is burned up, he will suffer loss; but he himself will be saved, yet so as through fire. Do you not know that you are a temple of God and that the Spirit of God dwells in you? If any man destroys the temple of God, God will destroy him, for the temple of God is holy, and that is what you are."'
Note that in this passage, believers are compared to a building. The foundation of our salvation is Jesus Christ. What we do in this life to serve God (the building) will be tested when we go to heaven. If we have not served God, which would include a believer continuing in sin, then our works will not pass the test. They will be like wood and straw, useless and burned up in the testing fire.
With nothing to show for our lives in service to God, we will still be saved (v. 15), but we will lose any potential rewards. If we have lived a life in service to God, bearing fruit that lasts, our work will be like gold and precious stones, surviving God's testing fire. This will lead to rewards in heaven. For more information on rewards, please read our Eternal Rewards series.
Finally, it's worth noting that not everyone who claims to be a believer is truly saved. Occasionally, someone may claim to be a Christian when they have not truly been born again by faith in Jesus Christ. In such a case, the person will continue sinning without repentance because they lack the Holy Spirit to convict them or the new nature that seeks to please God. Since it may not be possible to discern the difference between a disobedient Christian and an unbeliever who continues in sin, we should refrain from making judgments or drawing conclusions concerning a person's salvation based solely on their behavior.
A Believer Can Not Turn His Back on the Lord
Source: https://www.versebyverseministry.org/bible-answers/can-someone-continue-in-sin-and-still-be-saved