Can you explain what “if we sin willfully” in Hebrews 10:26 means?

Answer:

The English Standard Version that you quoted from is trying to make this clear. "Sinning" (hamartanonton) is an active present participle in the Greek. It is something that you are presently, actively doing. That is why the ESV added "go on" to "sinning" in order to show that continuing state of deliberately being a sinner.

If a person deliberately stays in his sin, even though he has full knowledge that his sin is wrong, what is left to convince him that he needs to leave his sins behind?

"For it is impossible for those who were once enlightened, and have tasted the heavenly gift, and have become partakers of the Holy Spirit, and have tasted the good word of God and the powers of the age to come, if they fall away, to renew them again to repentance, since they crucify again for themselves the Son of God, and put Him to an open shame" (Hebrews 6:4-6).

This is another passage that is often misapplied. Many want to read this and say that once I've sinned, God won't let me come back. But the statement is directed to those trying to bring a sinner back to God. He is telling teachers of the gospel that when you are dealing with a person who knows the truth and who deliberately goes into sin and chooses to stay there, that we have an impossible task on our hands. Since the sinner knows the truth and stays in sin anyway, there isn't anything else to offer them to convince them to leave their sin. This doesn't mean they can't or won't leave their sin. God still wants them (II Peter 3:9) and they can still choose to leave their sin. But it has to be the sinner's choice. I, as a teacher, cannot renew them to repentance.

It comes back to the question Paul once asked, "What shall we say then? Shall we continue in sin that grace may abound? Certainly not! How shall we who died to sin live any longer in it?" (Romans 6:1-2). A person cannot be saved while continuing to live in sin. Following Christ is about removing sin from our lives, not wallowing in it. "Knowing this, that our old man was crucified with Him, that the body of sin might be done away with, that we should no longer be slaves of sin" (Romans 6:6).

None of this is referring to a Christian who sins accidentally, or in a moment of weakness deliberately goes against what he knows to be right. God has proved an avenue of forgiveness:

"If we say that we have no sin, we deceive ourselves, and the truth is not in us. If we confess our sins, He is faithful and just to forgive us our sins and to cleanse us from all unrighteousness. If we say that we have not sinned, we make Him a liar, and His word is not in us. My little children, these things I write to you, so that you may not sin. And if anyone sins, we have an Advocate with the Father, Jesus Christ the righteous" (I John 1:8-2:1).

But when a person deliberately stays in his sin, despite knowing that it is wrong, it becomes an entirely different matter. For example, there are people involved in various sexual sins such as fornication, adultery, or homosexuality. When I point out that what they are doing is sinful, a common response is "I know it is wrong, but I'm sure God would want me to be happy and He will overlook this." This is the type of person God is saying is in deep trouble.