"1 Beloved, do not believe every spirit, but test the spirits to see whether they are from God, for many false prophets have gone out into the world."
This verse assumes that not all who claim to speak from God are actually from God. It is clear from the passage that not only do false prophets exist, but they are actively in the world trying to deceive the elect. The question then is how do we know if a prophet is genuine. We are told three things about them:
They do not believe in the incarnation of the Lord Jesus Christ (v2-3)
"2 By this you know the Spirit of God: every spirit that confesses that Jesus Christ has come in the flesh is from God, 3 and every spirit that does not confess Jesus is not from God. This is the spirit of the antichrist, which you heard was coming and now is in the world already."
The key point in this passage is that "every spirit that confesses that Jesus Christ has come in the flesh is from God”. This calls back to what is said in the first chapter: "That which was from the beginning, which we have heard, which we have seen with our eyes, which we looked upon and have touched with our hands, concerning the word of life— the life was made manifest, and we have seen it, and testify to it and proclaim to you the eternal life, which was with the Father and was made manifest to us...” This is central to the message of the gospel. God became man. Those who don’t believe and confess this truth are not from God.
They are popular in the world because they have the same message as the world (v4-5)
"4 Little children, you are from God and have overcome them, for he who is in you is greater than he who is in the world. 5 They are from the world; therefore they speak from the world, and the world listens to them."
Christians ultimately overcome the deception of world and its agents because we have Christ. We hear the voice of the Shepherd and can distinguish it from the sweet seductive voices of the wolves of this world. We are able to do this because “because (we) are strong, and the word of God abides in (us), and (we) have overcome the evil one ” - 1 John 2:14. In recent times a lot of worldly principles have sneaked into christian doctrine. We sometimes celebrate greed and selfishness in the name of blessing and empowerment and in so doing we neglect the material and spiritual needs of those who struggle in our midst. We need to go back and continually feed on God’s Word so that we are strengthened to overcome. The best way to recognize what is counterfeit is increased familiarity with the authentic Word of God.
They do not listen to authentic gospel as preached by the Apostles (v6)
"6 We are from God. Whoever knows God listens to us; whoever is not from God does not listen to us. By this we know the Spirit of truth and the spirit of error."
The “we” here I think refers to the combined witness of the Apostles and those to whom they are writing (and by extension all christians). It seems like a callback to Chapter 1: "that which we have seen and heard we proclaim also to you, so that you too may have fellowship with us; and indeed our fellowship is with the Father and with his Son Jesus Christ”. We have fellowship with God because we listened and believed the witness of the Apostles. We in turn proclaim that gospel and whoever does not agree with that witness, that Jesus Christ our Lord left his throne in heaven to die for our sins so we can have life eternal, shows themselves to be false.
There are many different gospels being preached. There are many different people who all claim to be sent from God. But not all who claim to speak from God are actually from God. Let us draw near to God’s Word and test that what we hear is in line with Scripture.