The mark distinguishing the one spirit from the other is confession of faith. The former confesses Jesus Christ; the latter denies Him. The former is stronger than the latter. Therefore the believer conquers the deceivers, or false prophets.
The word of the latter comes from the world, and the world receives it. The word of the former is received by those who are from God.
The starting point for explaining the chief concept here is the concept of a false prophet, or false prophets, in the verse under consideration. True prophets uttered their prophecies while being moved by the Holy Spirit (2 Pet 1:21).
The source of the revelations which they uttered, or foretold, as prophets, is the Holy Spirit, or the Spirit of God. He animates, or moves, the prophet. Therefore the prophet spoke his words not from himself, but from the Spirit.
Or rather, his words were not his own, but the Spirit's. More precisely, they were the words both of the Spirit and of him (cf. 2 Pet 1:21 and the note).
Since in each prophet, besides the divine Spirit who animated him, there was also his own human spirit proper to him, there were many spirits among the many prophets. Therefore the Apostle speaks not of one spirit, but of spirits from God.
The same holds in another respect, with regard to false prophets. They too stood under the influence of a spirit. Yet it was a spirit not from God and not from truth, but the spirit of antichrist (1 Jn 4:3), from the devil (1 Jn 3:8).
It was the spirit of deception, or delusion, acting in the deceivers (1 Jn 2:26), or in the false prophets of whom the Apostle speaks here. This spirit animates them and lives in them, as though united, or made akin, to their spirit.
These spirits not from God were also many, according to the number of persons animated by them, just as there were many false prophets. Therefore both the spirits from God and the spirits not from God were many.
For this reason the Apostle speaks of testing not the spirit, but the spirits.
If we translate the Apostle's inspired language into simple, ordinary speech, his words under explanation may and must be paraphrased thus. Beloved, do not believe every teacher or prophet who teaches as though by divine inspiration, or by prompting from the Spirit of God.
Nor believe everyone who presents himself as enlightened by the Spirit of God. Rather, test carefully and prudently whether the teacher truly speaks a word from God. Test whether he truly preaches God-inspired and indisputably true teaching.
Test whether he is speaking words suggested by the spirit of deception and fraud.
"After explaining the teaching on love of neighbor, and after pointing to this love as the sign of the abiding of the Spirit whom we have received, the Apostle now adds a sign for distinguishing true brethren and neighbors.
"He does this so that, keeping this distinction in view, we may not, on account of the commandment of love, enter into close relations with false brethren, false apostles, and false prophets, and thereby cause ourselves great harm.
"For if we have communion with them as with those of like mind, we shall first harm ourselves, by fearlessly communicating the teaching of faith to the impious and casting holy things to dogs.
"Then we shall harm those entrusted to us. For our love toward false brethren, false prophets, and false apostles will dispose many to accept them as teachers and to believe their teaching without caution. They will then fall into deception because of our association with them" (Theophylact).
In the primitive Church, among the faithful, there were people who possessed the extraordinary spiritual gift of discerning spirits (1 Cor 12:10). Without doubt the Apostle has this gift, or those who possess it, in view here.
Yet since he speaks to all the faithful in the Church without distinction, commanding them to test the spirits, whether they are from God, this extraordinary gift alone is surely not meant here.
Rather, he means in general the gift, or capacity, of wise insight and penetration into the truth of Christian doctrine and faith.
The Apostle indicates the reason why he commands believers to test teachers and their teaching. It is that many false prophets have appeared in the world. Those who preach doctrine are not only teachers enlightened by the Spirit of God.
There are also false teachers who are strangers to the Spirit from God. The Apostle calls them deceivers (1 Jn 2:26), and the Apostle Peter calls them false teachers (2 Pet 2:1).
They falsely appropriate to themselves the gift of prophecy or the gift of teaching; see the note on 2 Pet 2:1. These teachers, or false teachers, have appeared in the world.
Many of them have appeared, like tares in the field among the wheat (Mt 13:25-26). It is against them that the Apostle directs his discourse.
THEOSIS