Scripture isn’t all good news—it also conveys some serious threats.
As we consider the fundamentals of our faith, it’s clear the Lord has set forth some truths that cannot be trifled with. While God’s Word offers many glorious promises for believers who affirm and embrace essential gospel truths, it also warns of damnation for those who deny certain doctrines.
But today’s popular preaching philosophy echoes that corny old song: “You got to accentuate the positive, eliminate the negative, and latch on to the affirmative.” The problem with that philosophy is you can’t simply eliminate the negative when it comes to God’s Word. Biblical prohibitions don’t go away because we decide to ignore them.
Imagine you’re on a road trip. You’ll never successfully reach your destination if you ignore all the road signs, especially if some of those warn of danger. You need to know how to get there but you also need to know the hazards to avoid along the way. Likewise, we must heed God’s clear warnings while traveling the narrow road to eternal life.
In his book Reckless Faith, John MacArthur explains how the prohibitions in Scripture shape essential doctrines:
Certain teachings of Scripture carry threats of damnation to those who deny them. . . . Such doctrines, obviously, involve fundamental articles of genuine Christianity.
The apostle John began his first epistle with a series of statements that establish key points of the doctrine of sin (hamartiology) as fundamental articles of faith. “If we say that we have fellowship with Him and yet walk in the darkness, we lie and do not practice the truth” (1 John 1:6). That condemns wanton antinomianism (the idea that Christians are under no law whatsoever) and makes some degree of doctrinal and moral enlightenment essential to true Christianity. A second statement rules out the humanistic notion that people are basically good: “If we say that we have no sin, we are deceiving ourselves, and the truth is not in us” (1 John 1:8). And a third suggests that no true Christian would deny his or her own sinfulness: “If we say that we have not sinned, we make Him a liar, and His word is not in us” (1 John 1:10).  John MacArthur, Reckless Faith (Wheaton: Crossway, 1994) 112–113.
The apostle’s words draw a clear line of distinction between true and false professions of faith. At the heart of this distinction is the doctrine of repentance. Those who profess faith in Christ but deny Him through persistent sinful lifestyles are lying about their faith. Conversely, those who deny their sin are actually calling Jesus Christ a liar. Either way it is damnable denial.
John MacArthur also warns of the danger in denying Jesus Christ the love He is so worthy to receive: “First Corinthians 16:22 makes love for Christ a fundamental issue: ‘If anyone does not love the Lord, let him be accursed.’”  Reckless Faith, 113.
Moreover, our love must be biblical, and not merely directed at a “christ” of our own design:
The truth of Jesus’ incarnation is also clearly designated a fundamental doctrine: “Every spirit that confesses that Jesus Christ has come in the flesh is from God; and every spirit that does not confess Jesus is not from God; and this is the spirit of the antichrist” (1 John 4:2–3). “For many deceivers have gone out into the world, those who do not acknowledge Jesus Christ as coming in the flesh. This is the deceiver and the antichrist” (2 John 7). Those verses by implication also condemn those who deny the Virgin Birth of our Lord, for if He was not virgin-born, He would be merely human, not eternal God come in the flesh.  Reckless Faith, 113.
That God came and dwelt among us in human flesh (John 1:14) is both an historical fact and essential doctrine. Denial amounts to a rejection of His saving work performed on our behalf (2 Corinthians 5:21).
Additionally, Scripture pronounces damnable curses on anyone who adds to, subtracts from, or distorts God’s written Word (Revelation 22:18–19). We must be reverent in our study of the Bible, and careful how we represent its truth to others (2 Timothy 2:15). As John MacArthur explains, even the way we handle Scripture can invite the wrath of God:
And since those who twist and distort the Word of God are threatened with destruction (2 Peter 3:16), it is evident that both a lofty view of Scripture and a sound method of Bible interpretation (hermeneutics) are fundamental tenets of true Christianity.  Reckless Faith, 113.
Christianity is more than just the sum of the basic truths you can affirm. Just as important are Scripture’s warnings of denying fundamental truths. Thankfully, God loves us enough to warn of the eternal danger facing those who deny those truths regarding His character, His Son, and His Word.