Beloved, believe not every spirit - Do not confide implicitly in everyone who professes to be under the influences of the Holy Spirit. Compare Matthew 24:4-5. The true and the false teachers of religion alike claimed to be under the influence of the Spirit of God, and it was of importance that all such pretensions should be examined. It was not to be admitted because anyone claimed to have been sent from God that therefore he was sent. Every such claim should be subjected to the proper proof before it was conceded. All pretensions to divine inspiration, or to being authorised teachers of religion, were to be examined by the proper tests, because there were many false and delusive teachers who set up such claims in the world.
But try the spirits whether they are of God - There were those in the early Christian church who had the gift of “discerning spirits,” (see the notes at 1 Corinthians 12:10), but it is not certain that the apostle refers here to any such supernatural power. It is more probable, as he addresses this command to Christians in general, that he refers to the ability of doing this by a comparison of the doctrines which they professed to hold with what was revealed, and by the fruits of their doctrines in their lives. If they taught what God had taught in his word, and if their lives corresponded with his requirements, and if their doctrines agreed with what had been inculcated by those who were admitted to be true apostles, 1 John 4:6, they were to receive them as what they professed to be. If not, they were to reject them, and hold them to be impostors. It may be remarked, that it is just as proper and as important now to examine the claims of all who profess to be teachers of religion, as it was then. In a matter so momentous as religion, and where there is so much at stake, it is important that all pretensions of this kind should be subjected to a rigid examination. No one should be received as a religious teacher without the clearest evidence that he has come in accordance with the will of God, nor unless he inculcates the very truth which God has revealed. See the Isaiah 8:20 note, and Acts 17:11 note.
Because many false prophets are gone out into the world - The word prophet is often used in the New Testament to denote religious instructors or preachers. See the notes at Romans 12:6. Compare the notes at 2 Peter 2:1. Such false teachers evidently abounded in the times here referred to. See the notes at 1 John 2:18. The meaning is, that many had gone out into the world pretending to be true teachers of religion, but who inculcated most dangerous doctrines; and it was their duty to be on their guard against them, for they had the very spirit of antichrist, 1 John 4:3.