How can a Christian who committs suicide still go to Heaven? Doesn't the Bible say that sin cannot enter Heaven, and since a Christian needs to repent of sin to receive salvation but a person who commits suicide can't repent, then how can they still go to Heaven?
Every Christian entertains sinful thoughts and behaves in sinful ways on a regular basis, for such is the condition of our flesh, but these thoughts and actions do not disqualify us from Heaven. We are required to repent as a part of our salvation moment, but repentance on a continual basis is not the basis for our entry to Heaven.
First, if we say continual confession of sin is required to ensure our salvation, then we are saying that salvation is conditional on works (i.e., the work of continual confession). More over, how could anyone pass this test so as to enter Heaven? Consider what would happen to any Christian who utters a curse word or entertains a sinful thought in the moment before they die in a sudden car crash or of a heart attack? Wouldn't this person be excluded from Heaven? How could any of us feel secure in our salvation if Heaven were entirely dependent on the good timing of our death?
If we believe a Christian who commits suicide dies without hope of Heaven, then we must conclude that most (if not all) Christians have likewise lost the promise of eternal life because they too will have failed to repent of a specific sin before they died. If continuous confession of sin is a requirement for salvation, then every Christian lives in constant jeopardy.
Thankfully, God has provided a more powerful salvation that is by grace alone and not by works. Though we may die with some unconfessed sin, nevertheless we still enter into Heaven because our salvation is based on receiving Christ's righteousness and not based on our own perfection. We can know this is true by studying what the Bible says about our sin and the nature of our salvation.
For example, you correctly stated that sin cannot enter heaven, but the Bible says all men have sinned and fall short of the glory of God. Therefore, God must remove our sin and give us His righteousness if we are to enter Heaven. Without the righteousness of God, we would have no hope. By faith, the Father assigns Christ's righteousness to us. His sinlessness is awarded to us on the basis of faith alone, so we acquire the perfection required to enter Heaven based on Christ's perfection and not our own.
Christ also paid the penalty for our sin when He died in our place on the cross. So, a great exchange takes place. Christ takes our sin on the cross, while we receive His righteousness as a gift. As Paul says:
2Cor. 5:21 He made Him who knew no sin to be sin on our behalf, so that we might become the righteousness of God in Him.
Phil. 3:9 and may be found in Him, not having a righteousness of my own derived from the Law, but that which is through faith in Christ, the righteousness which comes from God on the basis of faith.
So our entrance into Heaven is made possible solely on the basis of our faith in Christ's death and resurrection, which brings us Christ's righteousness.
How does repentance factor into our salvation? The Bible calls on all people to repent and believe in order to receive this gift of eternal life, but the repentance the Bible is speaking about is a one-time turning from dead works and turning toward Christ in faith, as Hebrews says:
Heb. 6:1 Therefore leaving the elementary teaching about the Christ, let us press on to maturity, not laying again a foundation of repentance from dead works and of faith toward God.
The repentance to obtain eternal life does NOT mean repenting of each and every individual sin in our lives. Eternal life does not depend on listing out our sins and confessing each one in turn. Every Christian has literally thousands of unconfessed sins, and we have probably forgotten far more sin than we could ever remember, much less confess! Simply put, such a behavior isn't even possible must less required for salvation.
Instead, the repentance that leads to eternal life is an unique kind of repentance. Our one-time moment of repenting of our life of dead works and accepting Jesus Christ saves us for all time by bninging us Christ's righteousness. From the point of our confession in faith, every Christian is assured Heaven, because we have Christ's righteousness and no amount of sin can exceed the grace of God. Simply put, we can't sin our way out of God's grace and mercy once we have been clothed in His righteousness.
Therefore, repenting and confessing every sin in our daily lives is not a prerequisite for entering Heaven. Again, if such a requirement existed, then no Christian could ever enter Heaven, for we all live with unconfessed sins everyday of our lives. (To learn more about the role of repentance in the life of a believer, we encourage you to read our article: Do Christians need to ask for forgiveness?)
A true Christian who commits suicide will still enter Heaven, because this person was saved at the point of their confession of Christ, and no sin can ever separate a Christian from the love of God, not even the sin of self-murder. Every Christian bears the righteousness of Christ forever more. As Paul says:
