What exactly is an unbeliever?

Response

A “believer” is a child of God, reborn through faith in Jesus Christ (see Acts 2:44); an “unbeliever” is someone who does not have faith in Jesus. In the New Testament, the Greek word apistou is translated as “unbeliever.” Its adjective form literally means “not faithful,” describing someone who lacks Christian faith.

The Bible consistently distinguishes between those who follow Christ and those who do not. The term “unbeliever” was used to represent everything contrary to Christian faith and righteousness. In 2 Corinthians 6:14–15, Paul advises, “Do not be unequally yoked with unbelievers. For what partnership has righteousness with lawlessness? Or what fellowship has light with darkness? What accord has Christ with Belial? Or what portion does a believer share with an unbeliever?” The belief was that those who had faith in Christ were being transformed into His image “For those God foreknew he also predestined to be conformed to the image of his Son, that he might be the firstborn among many brothers and sisters.”, (Romans 8:29). The more they progressed in this transformation, the fewer similarities they had with unbelievers.

Regarding salvation, the term “believe” implies more than just agreeing mentally with the truth (John 3:16; John 14:1; 1 John 3:23; Acts 8:37). Even Satan and the demons have knowledge about Jesus, His death, resurrection, and the truth of Scripture “You believe that there is one God. Good! Even the demons believe that—and shudder.”, (James 2:19). Believing for salvation

«For with the heart, man believes unto righteousness; and with the mouth, confession is made unto salvation.», (Romans 10:10) requires more than that. A believer is one who has transferred ownership of his life and future to the lordship of Jesus. Jesus said, “You are my friends if you do what I command you” «Ye are my friends, if ye do whatsoever I command you.», (John 15:14). So a believer, in the biblical sense, is one who has responded to God’s calling and chosen Jesus as the Lord of his or her life. A believer looks to Jesus alone for salvation from sin and hell (John 14:6; Matthew 10:28; Romans 10:13). By the same token, an unbeliever is someone who has not allowed Jesus to be the Lord of his or her life. Religious-sounding words may have been spoken, but if the heart has not changed, it is not saving faith (Matthew 7:21-23). The person claiming salvation while lacking evidence of the transforming power of the Holy Spirit is still functionally an unbeliever.

When Scripture compares believers with unbelievers, it highlights the lifestyle differences. Believers are to be known by their love «By this shall all men know that ye are my disciples, if you have love one to another.», (John 13:35), their holiness «but as he which hath called you is holy, so be ye holy in all manner of conversation;», (1 Peter 1:15), and their desire to be like Christ «but speaking the truth in love, may grow up into him in all things, which is the head, even Christ:», (Ephesians 4:15). According to the entirety of Scripture, it is impossible to be a genuine believer and persist in the ungodly behaviors that provoked God’s wrath initially (Ephesians 5:5-7). This is because salvation leads to a new nature «Therefore if any man be in Christ, he is a new creature: old things are passed away; behold, all things are become new. », (2 Corinthians 5:17). Just as a fish cannot survive on land for long due to its nature, born-again hearts cannot persist in sin for long due to their new nature.

First John 3:6 explains it clearly: “No one who lives in him keeps on sinning. No one who continues to sin has either seen him or known him.” Then verses 8–10 further clarify: “The one who does what is sinful is of the devil, because the devil has been sinning from the beginning. The reason the Son of God appeared was to destroy the devil’s work. No one who is born of God will continue to sin, because God’s seed remains in them; they cannot go on sinning, because they have been born of God. This is how we know who the children of God are and who the children of the devil are: Anyone who does not do what is right is not God’s child, nor is anyone who does not love their brother and sister.”

“Without faith it is impossible to please God” «But without faith it is impossible to please him: for he that cometh to God must believe that he is, and that he is a rewarder of them that diligently seek him. », (Hebrews 11:6); therefore, unbelievers cannot please God. They are still dead in their transgressions and sins «And you hath he quickened, who were dead in trespasses and sins; », (Ephesians 2:1). Unbelievers still bear the full weight of all their sin, and the “wrath of God remains on them” «He that believeth on the Son hath everlasting life: and he that believeth not the Son shall not see life; but the wrath of God abideth on him.», (John 3:36). They must be reconciled to God through Christ «For if, when we were enemies, we were reconciled to God by the death of his Son, much more, being reconciled, we shall be saved by his life. », (Romans 5:10). Faith makes all the difference. Only through faith and surrender to the lordship of Jesus Christ can unbelievers become believers.