Can a believer forfeit eternal life by sinning? The answer is found in many scriptures, such as the following, which all guarantee that those who practice various sins will not inherit God’s kingdom. If a believer can return to the practice of the sins in the following lists compiled by Paul, then a believer can forfeit ultimate salvation:
Do you not know that the unrighteous shall not inherit the kingdom of God? Do not be deceived; neither fornicators, nor idolaters, nor adulterers, nor effeminate, nor homosexuals, nor thieves, nor the covetous, nor drunkards, nor revilers, nor swindlers, shall inherit the kingdom of God (1 Cor. 6:9-10, emphasis added).
Now the deeds of the flesh are evident, which are: immorality, impurity, sensuality, idolatry, sorcery, enmities, strife, jealousy, outbursts of anger, disputes, dissensions, factions, envying, drunkenness, carousing, and things like these, of which I forewarn you just as I have forewarned you that those who practice such things shall not inherit the kingdom of God (Gal. 5:19-21, emphasis added).
For this you know with certainty, that no immoral or impure person or covetous man, who is an idolater, has an inheritance in the kingdom of Christ and God. Let no one deceive you with empty words, for because of these things the wrath of God comes upon the sons of disobedience (Eph. 5:5-6, emphasis added).
Notice that in every case, Paul was writing to believers, warning them. Twice he warned them to not be deceived, indicating that he was concerned that some believers might think that a person could practice the sins he listed and still inherit God’s kingdom.
Jesus warned His closest disciples, Peter, James, John and Andrew of the possibility of their being cast into hell because of not being ready for His return. Note that the following words were addressed to them (see Mark 13:1-4), and not to a crowd of unbelievers:
Therefore be on the alert, for you do not know which day your Lord is coming. But be sure of this, that if the head of the house had known at what time of the night the thief was coming, he would have been on the alert and would not have allowed his house to be broken into. For this reason you [Peter, James, John and Andrew] be ready too; for the Son of Man is coming at an hour when you [Peter, James, John and Andrew] do not think He will.
Who then is the faithful and sensible slave whom his master put in charge of his household to give them their food at the proper time? Blessed is that slave whom his master finds so doing when he comes. Truly I say to you, that he will put him in charge of all his possessions. But if that evil slave says in his heart, “My master is not coming for a long time,” and shall begin to beat his fellow slaves and eat and drink with drunkards; the master of that slave will come on a day when he does not expect him and at an hour which he does not know, and shall cut him in pieces and assign him a place with the hypocrites; weeping shall be there and the gnashing of teeth (Matt. 24:42-51; emphasis added).
The moral of the story? “Peter, James, John and Andrew, don’t be like the unfaithful servant in this parable.”
To underscore what He just said to His closest disciples, Jesus immediately continued with the Parable of the Ten Virgins. All ten virgins were initially ready for the coming of the bridegroom, but five become unready and were excluded from the wedding feast. Jesus ended the parable with the words, “Be on the alert then [Peter, James, John and Andrew], for you [Peter, James, John and Andrew] do not know the day nor the hour” (Matthew 25:13). That is, “Don’t be like the five foolish virgins, Peter, James, John and Andrew.” If there were no possibility of Peter, James, John and Andrew not being ready, there would be no need for Jesus to have warned them.
Jesus then immediately told them the Parable of the Talents. It was the same message again. “Don’t be like the one talent slave who had nothing to show for what his master entrusted to him when he returned.” At the end of the parable, the master declared, “Cast out the worthless slave into the outer darkness; in that place there shall be weeping and gnashing of teeth” (Matt. 25:30). Jesus could not have made His message clearer. Only a theologian could twist His meaning. There was a danger that Peter, James, John and Andrew could all be cast into hell in the end if they weren’t obedient when Jesus returned. If that possibility existed for Peter, James, John and Andrew, then that possibility exists for all of us. As Jesus promised, only those who do the will of His Father will enter the kingdom of heaven (see Matt. 7:21).
Those who teach the false doctrine of unconditional eternal security clearly work against Christ and assist Satan, teaching the opposite of what Jesus and the apostles taught. They effectively neutralize Jesus’ commandment to make disciples who will obey all He commanded, blocking the narrow road to heaven, and widening the broad highway to hell.
 Amazingly, some teachers, who can’t escape the facts that Jesus was warning His closest disciples and that the unfaithful servant clearly represents one who was a believer, say that the place of weeping and gnashing of teeth is a place in the outer fringes of heaven. There, unfaithful believers will supposedly temporarily mourn their loss of rewards until Jesus wipes the tears from their eyes and then welcomes them into heaven!
 Of course, Christians who commit a single sin do not immediately forfeit their salvation. Those who ask forgiveness for their sins are forgiven by God (if they forgive those who sin against them). Those who don’t ask for God’s forgiveness place themselves in the danger of being disciplined by God. Only by hardening their hearts to God’s on-going discipline do believers run the risk of forfeiting their salvation. We will more fully explore the subject of God’s discipline in a later chapter.
 Those who are still not persuaded that a Christian can forfeit his salvation should consider all of the following New Testament passages: Matt. 18:21-35; 24:4-5, 11-13, 23-26, 42-51; 25:1-30; Luke 8:11-15; 11:24-28; 12:42-46; John 6:66-71; 8:31-32, 51; 15:1-6; Acts 11:21-23; 14:21-22; Rom. 6:11-23; 8:12-14, 17; 11:20-22; 1 Cor. 9:23-27; 10:1-21; 11:29-32; 15:1-2; 2 Cor. 1:24; 11:2-4; 12:21-13:5; Gal. 5:1-4; 6:7-9; Phil. 2:12-16; 3:17-4:1; Col. 1:21-23; 2:4-8, 18-19; 1 Thes. 3:1-8; 1 Tim. 1:3-7, 18-20; 4:1-16; 5:5-6, 11-15, 6:9-12, 17-19, 20-21; 2 Tim. 2:11-18; 3:13-15; Heb. 2:1-3; 3:6-19; 4:1-16: 5:8-9; 6:4-9, 10-20; 10:19-39; 12:1-17, 25-29; Jas. 1:12-16; 4:4-10; 5:19-20; 2 Pet. 1:5-11; 2:1-22; 3:16-17; 1 John 2:15-2:28; 5:16; 2 John 6-9; Jude 20-21; Rev. 2:7, 10-11, 17-26; 3:4-5, 8-12, 14-22; 21:7-8; 22:18-19. The proof texts produced by those who teach the doctrine of unconditional eternal security are scriptures that simply emphasize God’s faithfulness in salvation, and say nothing about human responsibility. Thus they must be interpreted to harmonize with the many scriptures I’ve just listed. Just because God promises His faithfulness is no guarantee of anyone else’s faithfulness. Just because I promise my wife that I’ll never leave her and keep my promise, but that is no guarantee that she will never leave me.