Based on the sermon:

Faith Under Fire: Standing Guard Against the Enemy Within

In our comfortable Western churches, we often think of attacks on Christianity in terms of dramatic persecution—believers thrown to lions, martyrs facing the executioner’s block, or modern-day saints dying for their faith in hostile nations. While such external persecution certainly exists and demands our prayers, there’s another threat that may be even more dangerous: the enemy within.

The Two-Pronged Attack

Throughout history, Satan has employed two primary strategies to destroy the church. The first is persecution—direct, frontal assault from outside forces. When Saul of Tarsus dragged Christians from their homes to prison, when Roman emperors fed believers to wild beasts, when Islamic extremists today demand believers renounce Christ or die, this is persecution in its rawest form.

Remarkably, persecution often strengthens rather than weakens the church. As early church father Tertullian observed, “The blood of the martyrs is the seed of the church.” When unbelievers witness Christians willing to die for their faith, it causes them to wonder what could be worth such sacrifice. The church has historically grown strongest under persecution’s pressure.

But Satan’s second strategy is far more insidious: infiltration.

When the Enemy Looks Like a Friend

The book of Jude warns us about “certain persons” who have “crept in unnoticed”—false teachers who slip into the church like crocodiles entering water without making a ripple. These aren’t honest enemies attacking from without; they’re wolves in sheep’s clothing, claiming to be part of the family while slowly poisoning it from within.

This infiltration strategy operates like termites in a house’s foundation. The external structure may look solid while internal destruction silently proceeds. By the time the damage becomes visible, the entire structure may be compromised.

Consider Harvard University, founded in 1636 to train Puritan pastors for the gospel ministry. Today, its chaplain is a devout atheist. This didn’t happen overnight—it was a gradual drift, one compromise at a time, until an institution once dedicated to Christian truth became its enemy.

The Markers of Infiltration

Jude identifies three characteristics of these infiltrators:

They promote ungodliness. Despite claiming to follow Christ, their lives and teachings actively work against reverence for God. They may speak of spirituality, but it’s a spirituality divorced from biblical holiness.

They turn grace into a license to sin. These false teachers twist the beautiful doctrine of grace, suggesting that because we’re forgiven, moral standards no longer matter. They preach a cheap grace that costs nothing and changes nothing.

They deny the authority of Jesus Christ. Whether subtly or boldly, they reject Christ’s rightful lordship over their lives and teachings. They may acknowledge Jesus as a good teacher or moral example while denying His absolute authority as God incarnate.

The Poison in the Medicine Cabinet

In 1982, someone laced Tylenol capsules with cyanide and returned them to Chicago-area store shelves. Seven people died after taking what they thought was helpful medicine. This illustrates perfectly how false teaching works—it often sounds helpful, feels good, and appears beneficial while actually being deadly.

When popular teachers suggest that all paths lead to God, that the Bible contains errors, or that moral standards are outdated, they’re essentially putting poison in the medicine cabinet. People seeking spiritual help instead receive spiritual death.

Fighting for the Faith

So how do we respond? Jude’s answer is clear: “contend earnestly for the faith which was once for all handed down to the saints.” The Greek word he uses suggests an all-out struggle, fighting with every fiber of our being.

This isn’t about being mean-spirited or unloving. It’s about recognizing that truth matters. The Jesus of Mormonism is not the Jesus of the Bible. The Jesus of liberal theology is not the Jesus who saves. The Jesus who winks at sin is not the Jesus who died to deliver us from sin.

We must know what we believe and why we believe it. We must be able to distinguish between the true gospel and its counterfeits. We must love people enough to tell them the truth, even when it’s uncomfortable.

The Stakes Couldn’t Be Higher

Christianity is always just one generation away from extinction. Like runners in a relay race, each generation must successfully pass the baton of truth to the next. If we drop that baton—if we allow the faith to be corrupted or watered down—we have nothing of value to pass on to our children and grandchildren.

The question each of us must ask is this: Are we contending earnestly for the faith? Are we standing guard against both external persecution and internal corruption? Are we committed to preserving and passing on the pure gospel of Jesus Christ?

The church needs watchmen on the walls—believers who know the truth, love the truth, and will fight to preserve the truth. In an age of compromise and confusion, such faithfulness isn’t just admirable; it’s essential for the church’s survival and effectiveness.

The faith once delivered to the saints is worth fighting for. The question is: Will we?