25 This is the promise which He Himself made to us: eternal life. 26 These things I have written to you concerning those who are trying to deceive you. 27 As for you, the anointing which you received from Him abides in you, and you have no need for anyone to teach you; but as His anointing teaches you about all things, and is true and is not a lie, and just as it has taught you, you abide in Him. 28 Now, little children, abide in Him, so that when He appears, we may have confidence and not shrink away from Him in shame at His coming. 29 If you know that He is righteous, you know that everyone also who practices righteousness is born of Him. 1 John 2:25-29
No one can promise eternal life but Christ himself. The writer (the Apostle John) received this promise directly from him and is passing it on to us.
There were detractors in the “church” who thought otherwise. They left the fold to follow their own way. John was writing these things so that the followers of Christ might not be deceived.
Satan has devised many alternatives to the truth that sound plausible but are lies. He includes just enough truth to make his arguments enticing. We know this from his modus operandi with Jesus in the wilderness. (Matt. 4:1-11) Like Jesus, we know there’s something wrong because of our anointing, the Spirit of God within us who contemplates everything postulated and pronounces it true or false. We can rely on the teachings that come from within. John wrote of this confidence we should have in the truth, using the word four times in this letter.
While John had the privilege of hearing the truth directly from Jesus, we can read it in the Word, or in this case, in John’s letter. If we live, i.e. abide in the Word, it’s hard for heresy to penetrate and lead us astray. We have the textbook and the teacher. What more do we need?
Some scholars and skeptics obfuscate the truth with distracting questions about Bible authorship and accuracy, but the Spirit tells us “the sum of your word is true.” (Psalm 119:160) Our teacher does not let us veer into the weeds, but with His counsel he guides us.
I will instruct you and teach you in the way which you should go;
I will counsel you with My eye upon you. Psalm 32:8