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.1 John 2:27(NASB)
There are two insidious dangers to Christian fellowship and the growth of believers - 1) the infusion of the world into the Church and 2) the false teachers that deliver a false gospel. Both the world and false teachers can have a devastating effect on a believer's spiritual growth... but knowing biblical truth and being able to discern what is false is key to standing firm in this evil day.
John knows that any true born-again child of God is eternally secure, by grace through faith in Christ's sacrificial work at Calvary. Each one receives the anointing of the Holy Spirit at salvation when He comes to permanently indwell us and abide in us. This anointing happens the moment we trust Christ for our salvation - for we were bought with a price, the precious blood of Jesus Christ, and the cost of our redemption was paid in full - at Calvary.
Having received the anointing of God, the indwelling Spirit, and the abiding life of Christ Jesus our Lord, every believer has an assurance that those who walk in spirit and truth will be guided into all truth.
Christ Himself taught His disciples, only hours before His crucifixion, that the Advocate (the Holy Spirit) would be sent by the Father at His request. The Holy Spirit would teach believers all things and bring to our remembrance all that we have learned.
What a thrill to realise that once we are saved, we have the promise of the permanently indwelling Holy Spirit abiding in us... and He will never be taken from us. What a privilege to realise that when we are born from above and anointed by the Spirit of truth, He will teach us what we need to know, as we abide in Him, rest in His love, and trust His Word, in every area of our lives.
Some profess that this verse teaches that we do not need to study the Scriptures in order to be guided into all truth. Others use this as an excuse to be drawn into gnostic teachings which distort the truth of God's Word, by adding to, subtracting from, or distorting in various ways the gospel of God. Still others like to rely on extra-biblical dreams, visions, prophesies, mantras, and even YouTube videos to guide them in their Christian thinking... but this is not what John is teaching here.
John is simply saying that there is no illumination to be discovered that is additional to the inspired Word of God we hold in our hand. The Scriptures were specifically given to us from God for our learning. And together with the indwelling Holy Spirit living in our heart, we have all we need for our spiritual directives and development - as long we obey Christ's command to abide in Him and He in us. May we take this to heart as we die daily to our own desires and live each moment only for Him.
Heavenly Father, thank You for my salvation and the indwelling Holy Spirit. Thank You for the written Scriptures and the privilege of being in union with Christ, as part of His Body. I pray that I may be guided into all truth and given the wisdom and discernment to eschew what is evil and grow in understanding of the truth of the gospel, as I abide in Christ and He in me. This I ask in Jesus' name, AMEN.