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.
He returns to his former doctrine, which he had touched upon in the second chapter; for many (as it is usual in new things) abused the name of Christ for the purpose of serving their own errors. Some made a half profession of Christ; and when they obtained a place among his friends, they had more opportunity to injure his cause.
The apostle, having said that God's dwelling in and with us may be known by the Spirit that he hath given us, intimates that that Spirit may be discerned and distinguished from other spirits that appear in the world; and so here, I. He calls the disciples, to whom he writes, to caution and scrutiny about the spirits and spiritual professors that had now risen. 1.
Commenting on 1 John 4:1-3
Beloved, believe not every spirit,.... The apostle having mentioned the word "spirit" in the latter part of the preceding chapter, takes an occasion from thence to return to what he had been suggesting in the "second" chapter, concerning the many antichrists that then were, and whom he points out, and here cautions against.