There are many websites on the Internet that teach the once saved always saved doctrine. Here is how one of them explains it. The Bible teaches, “once saved always saved” — that we can be saved once and for all only through a repentant, saving faith in Jesus Christ. Once a person has accepted Christ as Savior, they may wonder if it is possible to lose that salvation. What if they commit a sin? What if they commit a lot of sins? What if they do something very, very wrong? Is it possible to be saved, and then lose that salvation? Fortunately, the answer is a resounding “no.” Once a person has accepted Jesus Christ as Savior, he/she is forever saved. This fact is referred to as the doctrine of “eternal security,” often summarized as “once saved always saved.” (https://www.allaboutgod.com/once saved always saved.htm) On the other hand, most websites that teach these doctrines use the death of Christ to support these doctrines. There are also many websites that reach how the eternal security doctrine is not Bible-based. This is one of them.
God’s Plan of Salvation
The authors of websites on the Internet that teach the once saved always saved doctrine do not fully understand God’s plan of salvation. They do not understand that there are two parts to the plan of salvation in the Bible. First, there is the salvation of the whole human race. (Luke 1:77) Second, there is the salvation of each person. (Hebrews 9:28)
The Salvation of the Human Race
It is so unfortunate that for most people, the phrase once saved always saved is often misused. This phrase can only apply to baptism. Baptism is forever; it cannot be lost or undone. The phrase should probably be once baptized always baptized. Baptism saves a person through the resurrection of Christ. (1 Peter 3:21) The blood of Christ caused God to pass over all past sins. (Romans 3:25; 2 Peter 1:9) Therefore, baptism saves a person from their past sins, not future sins. The salvation and security from past sins provided by baptism are eternal.
Having been made perfect, Christ became to all those who obey Him the source of eternal salvation. (Hebrews 5:9) This is the will of Him who sent Me, that of all that He has given Me I lose nothing but raise it up on the last day. For this is the will of My Father, that everyone who beholds the Son and believes in Him will have eternal life, and I Myself will raise him up on the last day. (John 6:39-40) True eternal salvation and security will be granted by Christ on the last day.
While enemies of God, He reconciled us to Him through the death of His Son. Moreover, since we have been reconciled, we shall now be saved by His life. (Romans 5:10) The life of our Christ, through whom we have now received the reconciliation. (Romans 5:11) So then, my beloved, work out your salvation with fear and trembling. (Philippians 2:12) Every epistle admonishes people who have been baptized to work out their salvation by following the will of God.
Salvation of each Person after Baptism
According to the bible, before baptism a person is once saved always saved from past sin. (Romans 3:25, 5:10) After baptism, the process of salvation by doing the will of God begins. He who has believed and has been baptized shall be redeemed. (Mark 16:16) Having been justified, we shall be redeemed. (Romans 5:9) Our spirit might be redeemed in the day of the Lord Jesus. (I Corinthians 5:5 The word of the cross to us who are being redeemed is the power of God. (I Corinthians 1:18) We are a fragrance of Jesus to God among those who are being redeemed. (2 Corinthians 2:15) Some did not receive the love of the truth so that they might be redeemed. (2 Thessalonians 2:10)
It is clear that those who endure until the end are once saved always saved people. (Matthew 10:22, 24:13, Mark 13:13) Moreover, Peter has the following message for people redeemed by baptism. Since Christ suffered in the flesh, arm yourselves with the same purpose, because those who have suffered in the flesh have ceased from sin, so that you live the rest of your time in the flesh to the will of the Lord. (I Peter 4:1-2)
Salvation by the Will of the Lord
It is clear that those who do the will of God are once saved always saved people. Whoever does the will of God will enter into heaven. (Matthew 7:21) Therefore, you need endurance, so that when you have done the will of the Lord, you may receive eternal life as promised. (Hebrews 10:36) The will of God is your sanctification. (1 Thessalonians 4:3) The will of the Lord is that by doing right you may silence the ignorance of foolish men. (1 Peter 2:15)
Keep the way of the Lord by doing righteousness and justice. (Genesis 18:19) When a man practices righteousness, he will save his life. (Ezekiel 18:27) You shall keep My Law, by which a man may live if he does them. (Leviticus 18:5, Nehemiah 9:29, Ezekiel 20:11, Ezekiel 20:13, Ezekiel 20:21) If you warned the righteous man that the righteous should not sin and he does not sin he shall surely live. (Ezekiel 3:21) When a man has practiced righteousness and has observed all My statutes and done them he shall surely live. (Ezekiel 18:19)
If a man observes all My statutes and practices righteousness, he shall surely live he shall not die. (Ezekiel 18:21) If a man turns away from all his transgressions that he has committed, he shall surely live he shall not die. (Ezekiel 18:28) If a man walks by the statutes that ensure life without committing iniquity, he shall surely live he shall not die. He has practiced righteousness he shall surely live. (Ezekiel 33:15-16) Moses writes that the man who practices the righteousness that is based on law shall live by that righteousness. (Romans 10:5) Whoever does the will of the Lord your God will live forever. (1 John 2:17)
The Will of the Lord
It is clear that those who keep the way of God are once saved always saved people. The will of the Lord and the way of the Lord are closely related. A person keeps the way of the Lord by doing righteousness. (Genesis 18:19) The will of God is what is good and acceptable and perfect. (Romans 12:2) The will of the Lord is your sanctification, that is, that you abstain from sexual immorality. (I Thessalonians 4:3) The will of God is that we live by doing what is right. (I Peter 2:15) People who suffer for the will of God will entrust their souls to Him in doing what is right. (1 Peter 4:19) The Bible makes it clear that the way of the Lord is certainly in the will of the Lord.
All unrighteousness is sin. (1 John 5:17) Saul, also known as Paul, filled with the Holy Spirit, fixed his gaze on Elymas, and said, “You who are full of all fraud and deceit, you son of Satan, you are an enemy of righteousness, will you not cease to make crooked the straight ways of God? (Acts 13:9-10) Therefore, do not believe in Satan when he tells you that you do not have to do all righteousness, because some righteousness has been abolished.
Apostasy After Baptism
It is clear that those who fall away after baptism are once saved always saved people. Eternal salvation or eternal security advocates want people to believe apostasy cannot happen. However, the Spirit explicitly says that in the last times some will fall away from the will of the Lord. They will instead obey spirits that tell lies. They will follow the teachings of demons. (1 Timothy 4:1) During that time, many believers will fall away. (Matthew 24:10) They will not allow the will of God deep into their souls. They keep it for only a short period. When persecution or trouble comes because of the teaching they accepted, they give up. (Mark 4:17) When people leave the way of Christ, can you make them change their lives again? People who once learned the truth received God’s gift and shared in the Holy Spirit. They hear God’s good message and see the great power of his new world. Once they leave it all behind, it is not possible to make them change again. That is because those who leave Christ are nailing him to the cross again, shaming him before everyone. (Hebrews 6:4-6)
According to the bible, the popular worldly doctrines of once saved always saved, eternal salvation/security erroneously refer to eternal life. Remember, it is the person who endures to the end that is saved (inherits eternal life). You certainly cannot lose what you have not inherited. However, based on the bible, you can lose eternal life.