(Heb 10:26-27) If we deliberately keep on sinning after we have received the knowledge of the truth, no sacrifice for sins is left, 27 but only a fearful expectation of judgment and of raging fire that will consume the enemies of God.
This is the only use of “truth” (aletheia) in Hebrews, but the writer is clearly speaking of the moment of our salvation. There’s certainly a sacrifice for sins available for the lost, if they’ll accept Jesus. But for those who’ve already obtained knowledge of the truth — who’ve accepted the gospel — rebellion exacts an awful price. See Heb 6:4-6.
“Truth” in James
(James 1:18) He chose to give us birth through the word of truth, that we might be a kind of firstfruits of all he created.
Again, plainly “truth” is what allows us to be born again. It’s the gospel.
(James 5:19-20) My brothers, if one of you should wander from the truth and someone should bring him back, 20 remember this: Whoever turns a sinner from the error of his way will save him from death and cover over a multitude of sins.
Thus, we should take “truth” here to also refer to the gospel. And rejecting the gospel — our faith in Jesus, our penitence — leads to death. This is the sort of error to which James is speaking.
“Truth” in 1 and 2 Peter
(1 Pet 1:22) Now that you have purified yourselves by obeying the truth so that you have sincere love for your brothers, love one another deeply, from the heart.
We are purified when we are saved, and thus “obeying the truth” is “obeying the gospel.”
(2 Pet 1:10-12) Therefore, my brothers, be all the more eager to make your calling and election sure. For if you do these things, you will never fall, 11 and you will receive a rich welcome into the eternal kingdom of our Lord and Savior Jesus Christ. 12 So I will always remind you of these things, even though you know them and are firmly established in the truth you now have.
Peter is discussing the importance of growing in the Christian virtues. If we continue to grow in them, our “calling and election” — our salvation — is sure. But Peter is saying this to his readers even though he considers them secure already — “firmly established in the truth,” that is, the gospel. We all need reminding.
(2 Pet 2:1-3) But there were also false prophets among the people, just as there will be false teachers among you. They will secretly introduce destructive heresies, even denying the sovereign Lord who bought them — bringing swift destruction on themselves. 2 Many will follow their shameful ways and will bring the way of truth into disrepute. 3 In their greed these teachers will exploit you with stories they have made up. Their condemnation has long been hanging over them, and their destruction has not been sleeping.
These false teachers will deny “the sovereign Lord” and so bring shame on “the way of the truth.” Plainly, “truth” means the truth about Jesus, the gospel, which includes, of course, his sovereignty as Lord.
And so we see a remarkable similarity in how the New Testament writers use “truth.” While it can sometimes be used of truth in general, most of the time, it means the most important truth, the truth about Jesus, the gospel. It’s the truth we have to believe and confess to be saved. It’s the truth that changes everything.
The several warnings against false teachers that speak of their denying the truth are speaking of teachers who deny the gospel, not the Bible’s teachings on instrumental music. And the truth that saves is the gospel: faith in Jesus, penitence, Jesus as Lord and Christ — not doctrines of church organization. My opinion or yours may well be true, but it’s not truth.
Just so, we’ve happened upon several warnings against falling away, and these are also described in terms of rejecting the truth.
The truth that sets us free, the truth that is Jesus, the truth that we must believe on penalty of damnation, is the gospel. It is nothing else. And this fact contradicts many (not all) of the favorite prooftexts being used to damn those who disagree over worship or whatever other hot button issues the Church periodicals are pounding.
More importantly, it tells us that any flat heremeneutic is wrong. Some truths found in the Bible are indeed much more important than others. Implicit in using “truth” to refer to a very narrow body of knowledge — the knowledge we gain while being converted — tells us what Jesus and the apostles considered to be the most important true thing —
(1 Cor 15:1-5) Now, brothers, I want to remind you of the gospel I preached to you, which you received and on which you have taken your stand. 2 By this gospel you are saved, if you hold firmly to the word I preached to you. Otherwise, you have believed in vain. 3 For what I received I passed on to you as of first importance: that Christ died for our sins according to the Scriptures, 4 that he was buried, that he was raised on the third day according to the Scriptures, 5 and that he appeared to Peter, and then to the Twelve.
If all doctrinal errors damn, then they are all equally important. But that’s just not what the Bible teaches. Indeed, the Bible tells us where our focus and teaching needs to be. The gospel is not only for the lost and new converts, it’s for us all, because the challenge is to live the gospel. And that’s the most important thing.