The letters of the apostle Paul are for us, believers from the nations, and addressed directly to us. We can read the letters of the other apostles, but they are not about us; they are intended for Israel. If we do apply the things we read there directly to ourselves, that is misplaced. They are biblical truths, but not if we apply them incorrectly.
Example
If we take a closer look at the passage in 2 Timothy where Paul speaks about rightly dividing the word of truth, this becomes even clearer. Paul himself gives an example of two people who did not rightly divide the word of truth:
2 Timothy 2
15 Do your best to present yourself approved to God, a worker who does not need to be ashamed, but rightly dividing the word of truth.
16 But avoid profane and empty speech, for it will only increase irreverence,
17 and their speech will spread like gangrene. Among them are Hymenaeus and Philetus,
18 who deviate from the truth and say that the resurrection has already taken place, thus destroying the faith of some.
Resurrection
The resurrection is a truth taught in Scripture. We find the resurrection described in detail by Paul in 1 Corinthians 15. There he speaks of the resurrection of Christ and what the result and scope of His resurrection will be: the making alive of all people (Cor. 15:22).
Misplaced
Hymenaeus and Philetus did not deny the resurrection, but they said that it had already taken place. They likely taught that the resurrection is an inner spiritual experience, rather than a physical reality. They reduced the resurrection to something already accomplished in this life and thus denied a future physical resurrection. They did not rightly divide the word of truth. Paul states that they thereby deviate from the truth (2 Tim. 2:18).
Serious
Paul takes this error very seriously. He doesn’t say things like, “You can think differently about that,” but condemns their teaching in harsh terms: “Their word will spread like gangrene.” Gangrene is a serious condition in which body tissue is affected and dies. The comparison with the ecclesia, the body of Christ, is quickly made.
The Law
Besides the previously mentioned examples, such as the words of Jesus during His earthly ministry and the words of the twelve apostles to the house of Israel, perhaps the clearest example of rightly dividing the word of truth is the principle of the law.
Galatians 3
24 So that the law has become our infant guide to Christ, so that we may be justified by faith.
25 But when faith comes, we are no longer under an infant guide.
pedagogue
The word translated “child guide” in verses 24 and 25 is the Greek word paidagogos. A pedagogue is an educator. We are no longer under this educator, under the law, says Paul. The law was given to one people: Israel, and for a specific time: from Moses to Christ.
The law was given until the Seed had come (verse 19). The Seed is Christ (verse 16). Now that faith has come (verse 25), namely, the faith of Jesus Christ (verse 22), we are no longer under the law, no longer under this educator. We are under grace (Rom. 6:14).
We should divide the word of truth correctly, divide it rightly. If we don’t do this, and live under the law, this is not correct, and we no longer have a word of truth!
A proven worker knows the truths of God’s word, believes them, and knows how to place them correctly.