Question: "If our salvation is eternally secure, why does the Bible warn so strongly against apostasy?"
Answer: The reason the Bible warns us so strongly against apostasy is that true conversion is measured by visible fruit. When John the Baptist was baptizing people in the Jordan River, he warned those who thought they were righteous to “bear fruits in keeping with repentance” (Matthew 3:7). Jesus warned those who were listening to Him while He was giving the Sermon on the Mount that every tree can be known by its fruit (Matthew 7:16) and that every tree that does not bear good fruit will be cut down and thrown into the fire (Matthew 7:19).
The purpose behind these warnings is to counter what some people would call “easy-believism.” In other words, following Jesus is more than saying you are a Christian. Anyone can claim Christ as Savior, but those who are truly saved will bear visible fruit. Now, one may ask the question, “What is meant by fruit?” The clearest example of Christian fruit can be found in Galatians 5:22-23 where Paul describes the fruit of the [Holy] Spirit: love, joy, peace, patience, kindness, goodness, faithfulness, gentleness, and self-control. There are other types of Christian fruit (such as praise, winning souls for Christ), but this list provides us with a good summary of Christian attitudes. True believers will manifest these attitudes in their lives to an increasing degree as they progress in their Christian walk (2 Peter 1:5-8).
It is these true, fruit-bearing disciples who have the guarantee of eternal security, and they will persevere to the end. There are many Scriptures that bear this out. Romans 8:29-30 outlines the “Golden Chain” of salvation by pointing out that those who were foreknown by God were predestined, called, justified, and glorified—there is no loss along the way. Philippians 1:6 tells us that the work God began in us, He will also finish. Ephesians 1:13-14 teaches that God has sealed us with the Holy Spirit as a guarantee of our inheritance until we possess it. John 10:29 affirms that no one is able to take God’s sheep out of His hand. There are many other Scriptures that say the same thing—true believers are eternally secure in their salvation.
The passages warning against apostasy serve two primary purposes. First, they exhort true believers to make sure of their “calling and election.” Paul tells us in 2 Corinthians 13:5 to examine ourselves to see whether we are in the faith. If true believers are fruit-bearing followers of Jesus Christ, then we should be able to see the evidence of salvation. Christians bear fruit in varying degrees based on their level of obedience and their spiritual gifts, but all Christians bear fruit; and we should see the evidence of that upon self-examination.
Now there will be periods in a Christian’s life where there is no visible fruit. These would be times of sin and disobedience. What happens during these times of prolonged disobedience is that God removes from us the assurance of our salvation. Note He doesn’t remove our salvation, but the assurance of it. That is why David prayed in Psalm 51 to restore to him the “joy of salvation” (Psalm 51:12). We lose the joy of our salvation when we live in sin. That is why we must examine ourselves. When a true Christian examines himself and sees no recent fruitfulness, it should lead to serious repentance and a returning to God.
The second primary reason for the passages on apostasy is to point out apostates. An apostate is someone who abandons his religious faith. It is clear from the Bible that apostates are people who made professions of faith in Jesus Christ, but never genuinely received Him as Savior. Matthew 13:1-9 (the Parable of the Sower) illustrates this point perfectly. In that parable, a sower sows seed onto four types of soil: hard soil, rocky soil, weed-choked soil, and freshly tilled soil. These soils represent four types of responses to the gospel. The first one is pure rejection, whereas the other three represent various levels of acceptance. The rocky soil and the weed-choked soil represent people who initially respond favorably to the gospel, but when persecution comes (rocky soil) or the cares of the world bear down (weed-choked soil), that person turns away. Jesus makes it clear with these two types of responses that though they initially accepted they never bore any fruit. Again, Jesus says in the Sermon on the Mount, “Not everyone who says, ‘Lord, Lord,’ will enter the kingdom” (Matthew 7:21).
It may seem unusual for the Bible to warn against apostasy, and at the same time to say that a true believer will never apostatize. However, this is what Scripture says. 1 John 2:19 specifically states that those who apostatize are demonstrating that they were not true believers. The Biblical warnings against apostasy, therefore, must be a warning to those who are “in the faith” without ever truly having received it. Scriptures such as Hebrews 6:4-6 and Hebrews 10:26-29 are warnings to “pretend” believers, that they need to examine themselves and realize that if they are considering apostatizing, they are not truly saved. Matthew 7:22-23 indicates that those “pretend believers” whom God rejects are rejected not because of having lost faith, but because of the fact that God never knew them.
There are many people who are willing to identify with Jesus. Who doesn’t want eternal life and blessing? However, Jesus warns us to count the cost of discipleship (Luke 9:23-26, 14:25-33). True believers have counted those costs, whereas apostates have not. Apostates are people who, when they leave the faith, give evidence they were never saved in the first place (1 John 2:19). Apostasy is not a loss of salvation, but rather a demonstration that salvation was never truly possessed.