Beloved, believe not every spirit, but try the spirits whether they are of God: because many false prophets are gone out into the world. 1 John 4:1.
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.... 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.... 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....
He declared what he knew, what he had seen and heard.... Out of the abundance of a heart overflowing with love for the Saviour he spoke; and no power could stay his words....
So may every true believer be able, through his own experience, to “set to his seal that God is true” (John 3:33). He can bear witness to that which he has seen and heard and felt of the power of Christ.34Ibid., 553-556.
From Conflict and Courage - Page 358
Conflict and Courage