On Apostasy

Sep 20, 2026 • Nathan Markley

SERMON SUMMARY:

Drawing from 2 Peter 2:17-22, this sermon confronts one of the most sobering realities addressed in Scripture: apostasy, defined as an enduring and deliberate departure from a prior devotion to Christ. The pastor navigates the tension between the doctrine of assurance, which affirms that true believers cannot be finally lost, and the genuine phenomenon of people who once appeared devoted to Christ walking away from the faith entirely. He clarifies that apostasy is distinct from doubt, depression, deconstruction, and ongoing sin, while also warning that any of these can become a downward slope if left unaddressed. The sermon calls the congregation to feel the full weight of apostasy, to pray for those who have walked away, and ultimately to keep reading, keep trusting, and keep growing in the grace and knowledge of Jesus Christ.

QUOTES:

Apostasy is enduring, deliberate departure from a prior devotion to Christ.

Once a person has been born again of the Spirit, you cannot ever become unborn.

The scripture says such people who fall away do not lose a salvation they once had. Rather, they never had that salvation to begin with.

Many people find that even if they are confused or hurt or even angry with God, even in that, they cannot seem to fully let go of God, even if part of them wants to. And that's a good sign that they're not letting go because God has not let them go.

It's easier to see when another dog is returning to its vomit than to recognize when we start to sniff around our own stuff ourselves.

Watching someone you love walk away from Jesus is enough to break your heart, to make you want to plead with them, to reason with them, to maybe grab them and shake them and shout at them and say, what are you doing? Don't you know the precious pearl that you're just throwing away?

We need to have these apostasies fully hit us, fully knock the wind out of our lungs so that we feel the crushing darkness of it.

It's as if the apostates who abandoned the Lord have become abandoned themselves.

There are even some things that happen churches that are not good either. People get deeply wounded and hurt by these things. Those things need to be brought to light and called into question.

A Christian is also not a person who mentally knows and decides to believe in God. And so if you decide to stop believing in God, then you stop being a Christian. At the root, a Christian is a child of God.

SCRIPTURE REFERENCES:

2 Peter 2:17-22, which describes false teachers as waterless springs, warns of the danger of returning to corruption after escaping it, and uses the proverbs of a dog returning to its vomit and a washed pig returning to the mud to illustrate apostasy

Hebrews 6:4-6, which describes the impossibility of restoring to repentance those who have fully fallen away after being enlightened and tasting the gifts of the Spirit

1 John 2:19, which teaches that those who depart from the faith demonstrate by their departure that they were never truly part of the community of genuine believers

KEY POINTS:

- Apostasy is an enduring, deliberate departure from a prior devotion to Christ. It is not the same as doubt, depression, deconstruction, or ongoing sin.

- The doctrine of assurance teaches that those who are truly born again cannot be finally or totally lost. Those who fall away ultimately reveal they were never truly in Christ to begin with (1 John 2:19).

- Doubt, depression, deconstruction, and ongoing sin are serious and should not be taken lightly, even though they are not apostasy. They can become a slope that leads toward it.

- Watching someone walk away from Jesus is a heartbreaking reality that calls us to prayer, patience, and grace.

The answer to the weight of apostasy is not despair but growth -- growing deeper in the grace and knowledge of Jesus Christ.

2 Peter 2:17-22

Hebrews 6:4-6

1 John 2:19

2 Peter 3:17-18

Hebrews 4:12

John 10:27-29

John 6:39

Luke 15:11-32

Luke 15:3-7

Matthew 26:69-75 / Mark 14:66-72 / Luke 22:54-62