A few years back, when I was working with the severely mentally ill, I was assigned a man with depression & drug addiction. A duel diagnosis. When I went to meet with him, it was obvious that he was into satanist activities, by the books on his shelf. He didn't believe in Jesus Christ as the risen savior, so I asked him, "If I can prove to you the existence of Jesus Christ as the risen savior, will you believe?" He said, if I could prove it he would.
I had no idea what a ride I was in for.
I got his attention enough that he agreed to go to church with me. He startled me by ending up on his face, on the floor, before the altar. He stood & held his hands towards the heavens & worshiped God. I didn't know whether to be excited or nervous. On the way home, he spoke of his new awakening. The Jesus had turned his life around.
Now, I'm semi excited, but, still weary. I know that God can do amazing things, but, something bothered me. He became a fixture a church. There every time the door opened. He joined a group I had started, a christian support group for the mentally ill, & actively participated. It looked like his life had truly changed.
One Saturday night at church, I heard the pastor ask him, "Who is you Lord." He stated, "Jesus". I knew this to be a test of the spirits. But, again, something in me felt wrong.
I John 1-6
1Dear friends, do not believe every spirit, but test the spirits to see whether they are from God, because many false prophets have gone out into the world. 2This is how you can recognize the Spirit of God: Every spirit that acknowledges that Jesus Christ has come in the flesh is from God, 3but every spirit that does not acknowledge Jesus is not from God. This is the spirit of the antichrist, which you have heard is coming and even now is already in the world.
His involvement with the church went on for about one month. He became inappropriate with myself one night and when corrected withdrew from the church. He began to use drugs again. A friend and myself decided to go & see him. On the way God told me not to say anything to him. I thought this would be a bit odd, but, told my friend & that is what we did.
We went into his home and sure enough, he did all the talking. But, while he was talking, I could feel a presence come into the room. My friend & I spoke later and we were having the same experience at the same time in this house. This presence was very heavy & evil. I would pray in my head & rebuke this thing & it would leave. But, then it would return. This went on the whole time we were there. This man just kept on talking about anything and everything unholy. We listened & rebuked for about 30 minutes.
Then the Lord told me to ask him this question. "What about Jesus?" His answer got myself & my friend to leave. He answered "I much more prefer my God to yours." Ok, that was it. Out the door.
God took me through this to show me several things. The most important, I believe, is that he said "Jesus is my Lord." So many Christians are under the impression that spiritually one can not say this who is not worshiping or following Jesus. But, I heard it with my own hears.
I came to the understanding that demons lie. They can lie about who they worship. So, what about testing spirits. We need to be testing spirits. We need to have the gift of discerning of spirits. The spirit that laid within this man, manipulated and lied his way into the church. The damage done was minimal. But, think about what could have been the outcome. Lives & reputations could have been destroyed.
I found the commentary below that I feel address this issue very well.
To understand John's instruction to test the Spirits, we need to place it in the context of Johannine church life. People met in houses in groups of about twenty to thirty people, for worship and fellowship (compare 2 Jn 10). These scattered communities did not have immediate access to authoritative figures like the Elder, and communication with them was not always easy. Apparently the Elder sent emissaries to communicate with the churches (3 John 5-8), sometimes carrying letters such as these epistles. These congregations had been glad to welcome the Elder's traveling ambassadors. But now there were also "false prophets" who, like the emissaries of the Elder, would have claimed to speak the truth under the inspiration of the Spirit. And, finally, there were also various itinerant philosophers who traveled in hopes of a hearing and a place to stay. In light of this complex situation, John is anxious to provide his readers with criteria against which claims to truth and inspiration could be tested.
Clearly the claim to be inspired by the Spirit can and must be tested, for the claim to have the Spirit is not proof that one does. Here spirit has been variously taken to refer to the spirit that inspires the prophet, to the person who is inspired or to the message delivered by the prophet. Obviously the three are related, for in testing a person's words one is actually testing whether or not that person speaks by divine guidance. In light of the rest of the passage two things emerge: First, the author believes that individual persons are inspired or led to confess or deny Christ by spirits, some reality beyond the human individual. Second, ultimately there are only two spirits: God's Spirit, also called the Spirit of truth because it guards and inspires truth (4:2, 6); and the spirit of antichrist, which inspires falsehood, and especially false confession of Christ (vv. 3, 6). The Elder's readers are not to believe every claim to be divinely inspired or to have a prophetic message, but are rather to test the spirits, to discern whether a message is the truth that comes from God. read more here