Hebrews 10:26 (NKJV)

For if we sin willfully after we have received the knowledge of the truth, there no longer remains a sacrifice for sins,

There are some who believe that this verse implies you can lose your salvation if you willfully sin after knowing everything about Christ.

Explanation

The context of this verse refers to those (non-believers) who left the church after hearing the gospel, seeing Christ’s claims in person, and being associated with His church to some extent.

These were people whose hearts had been warmed toward the gospel of Christ, who had made a superficial commitment of faith in Him, and who had identified themselves visibly with the true church.

Even so, their enthusiasm for Christianity faded, and the costs of being a Christian outweighed the benefits. As a result, they were ‘getting over’ the gospel, and were on the verge of becoming apostates.The context is not a believer who one day ceases to be a believer (or loses their salvation). That is a false teaching that contradicts hundreds of Bible passages that teach eternal security (see Jesus’ promise in Jn 10:27-29). Yet God’s infinite mercy does not turn a blind eye to deliberate sin, so we must never treat His grace and mercy as a license to live licentiously. 

Even though we are no longer under law, but under grace (Rom 6:14), grace is not a license to sin. Our lives will be filled with failures and falls, but they should never be the norm. Before we were saved we chased after sin, but now that we are saved, sin chases after us!

If an individual sinning willfully is a lifestyle, then that person must be very honest with himself or herself and ask, “Is my Christian profession a possession of Christ?” (2 Cor 13:5). This means that a person must examine whether their outward profession of faith is accompanied by a genuine, inward transformation. A mere acknowledgment of Christ without true conversion will result in a lifestyle that remains enslaved to sin, rather than reflecting the new creation that comes with true faith (2 Cor 5:17)

Incomprehensible truths such as Christ’s presence in us (Col 1:27) and His Spirit within us (1 Cor 6:19) enables us to resist committing willful sins (cf. 2 Cor 5:17) and enables us to combat temptations that assault our minds and entice us to commit that willful sin. 

Judas was the perfect prototype of an apostate. No other rejector of Christ was ever exposed to God’s truth, love, and grace as Judas. He was intimately familiar with the Lord. He was one of Jesus’ twelve inner circles of disciples. He would have become an apostle if he had believed, but he rejected the truth and became an apostate.

The story of Judas also contradicts the common excuse, “I would believe in Christ if I just had a little more evidence, a little more light.” Judas had the perfect proof, the perfect light, the perfect example. Although he lived with Truth incarnate and Life incarnate for some three years, he turned his back on the One who is truth and life. 

As we can see, this verse does not refer to a believer. Rather, it is speaking to a non-Christian, who knows about the gospel and is even intellectually convinced of its truth, but still lives  unrepentant and in willful sin. 

If a person rejects Christ despite knowing the truth of the gospel, there is certainly no hope for him.