As the years went by and the number of believers grew, John labored with increasing fidelity and earnestness for his brethren. The times were full of peril for the church. Satanic delusions existed everywhere. By misrepresentation and falsehood the emissaries of Satan sought to arouse opposition against the doctrines of Christ, and in consequence dissensions and heresies were imperiling the church. Some who professed Christ claimed that His love released them from obedience to the law of God. On the other hand, many taught that it was necessary to observe the Jewish customs and ceremonies; that a mere observance of the law, without faith in the blood of Christ, was sufficient for salvation.
Some held that Christ was a good man, but denied His divinity. Some who pretended to be true to the cause of God were deceivers, and in practice they denied Christ and His gospel. Living themselves in transgression, they were bringing heresies into the church. Thus many were being led into the mazes of skepticism and delusion.
John was filled with sadness as he saw these poisonous errors creeping into the church. He saw the dangers to which the church was exposed, and he met the emergency with promptness and decision. The Epistles of John breathe the spirit of love. It seems as if he wrote with a pen dipped in love. But when he came in contact with those who were breaking the law of God, yet claiming that they were living without sin, he did not hesitate to warn them of their fearful deception....
We are authorized to hold in the same estimation as did the beloved disciple those who claim to abide in Christ while living in transgression of God’s law. There exist in these last days evils similar to those that threatened the prosperity of the early church; and the teachings of the apostle John on these points should be carefully heeded. “You must have charity” is the cry heard everywhere, especially from those who profess sanctification. But true charity is too pure to cover an unconfessed sin. While we are to love the souls for whom Christ died, we are to make no compromise with evil. We are not to unite with the rebellious and call this charity. God requires His people in this age of the world to stand for the right as unflinchingly as did John in opposition to soul-destroying errors.... His testimony in regard to the Saviour’s life and death was clear and forcible. Out of the abundance of a heart overflowing with love for the Saviour he spoke; and no power could stay his words.—The Acts of the Apostles, 553-555. RC 66
If we venture on Satan’s ground we have no assurance of protection from his power. So far as in us lies, we should close every avenue by which the tempter may find access to us. Pr 301
"Whosoever committeth sin transgresseth also the law: for sin is the transgression of the law. And ye know that he was manifested to take away our sins; and in him is no sin." 1 John 3:4-5 (King James Version)