"Beloved, believe not every spirit," is a faithful translation of the original Greek. The first six verses of chapter 4 of the first epistle of John is a beacon of warning: love should be exercised with judgment and wisdom. We should love the believers, but we need to make sure that those who call themselves Christians are not false teachers or masters. Those who deny the incarnation of Christ are of these, and are revealed by the test.
This warning is given to the "beloved": the readers were not necessarily personal friends of John, but are loved by the Lord Jesus Christ who gave His life for them, and they love each other because "He who does not love his brother abides in death.” (1 John 3:14).
To believe, or not to believe, here involves the sense of a naive credulity: today as in the days when the letter was written by John, there is much deceit camouflaged as Christianity that absolutely has nothing spiritual, but that may deceive the misinformed; we also find today an abnormal concern with the occult by many Christians that is very dangerous; there is furthermore fanaticism in relation to personal ideas and interpretations that divides believers.
With regard to spirits, the Bible says, among other things: "... Of the angels He says, ‘who makes His angels spirits and His ministers a flame of fire.’" (Hebrews 1:7, quoting Psalm 104:4), and "Are they not all ministering spirits sent forth to minister for those who will inherit salvation?" (Hebrews 1:14). Above the ministry of angels, now we have the ministry of the Holy Spirit in our hearts and in our lives.
In contrast to these good angels who serve God there are fallen angels, also called “spirits” in Scripture. The Gospels speak much about the "unclean spirits" in the time of Christ. Their reality today is also admitted, and among them the main one, known as the devil or Satan is worshiped openly by his devoted priests and priestesses. As believers redeemed by the Son of God, Jesus Christ, we are exhorted by the Holy Spirit to protect ourselves with the whole armour of God because we are in a gigantic spiritual battle (Ephesians 6:12). Our enemies are well organized, like a powerful army.
John addressed this letter to his "little children", affectionately so calling those who are spiritually born again to hear and receive for themselves the gospel of Christ, of whom he was an apostle. As such we are instructed to love and help each other, but we need to be cautious: "And this I pray, that your love may abound still more and more in knowledge and all discernment" (Philippians 1:9). Science and knowledge give us discernment. It is wonderful to love, but we are in a great evil and malicious world, and it will deceive us if we let it.
There have always been false "masters". The Lord Jesus had warned the people against them (Matthew 7:15), even against false "christs" with their miraculous signs (Matthew 24:11,24, Mark 13:22). It is an old story (Luke 6:26) and appears occasionally in Scripture (eg Acts 13:6, Revelation 16:13, 19:20, 20:10). Now they are the leaders and false teachers, as there were false prophets among the Israelites (2 Peter 2:1). There are many teachers today who we must guard against because they are leaving aside what the Scriptures teach, or adding to them.
Just because someone comes to us saying the words "Jesus" or "Lord" a lot, or has graduated in theology or has ecclesiastical achievements does not mean that we must automatically love and trust him. This person may be even more dangerous than a snake because he teaches a false doctrine, or has little respect for the true doctrine. Although he may carry a Bible under his arm, he may not really be teaching God's Word.
The spirits, including masters and teachers, need to be tested, or proven to see whether they are from God. It is the acid test of truth, as a metallurgist does with his metals. If he passes the test, he is acceptable (2 Corinthians 10:18), otherwise he must be rejected (2 Corinthians 13:5-7). The test itself is very simple and gives an immediate result: every spirit that acknowledges that Jesus Christ (the Saviour sent by God) came to earth as a human being is of God. We must check if they admit the divinity of Jesus Christ (1 Corinthians 12:3), and the incarnation and resurrection of Christ (Romans 10:6-10).
Those who pass the test acknowledge that He is "the Word", God the Son, the Creator of all things, who made Himself flesh so fulfilling prophecies about the Messiah centuries before His birth, e.g. "unto us a Child is born, unto us a Son is given..." (Isaiah 9:6). The child was born, but the Son is given to us! The Son came from eternity, the Ancient of Days, while the human child was conceived in a virgin. His death and resurrection are meaningless unless He really was who He said He was, the Son of God transformed into man.
On the other hand, every spirit that denies the divine humanity of Jesus Christ, never comes from God. He is of the Antichrist. This word is mentioned earlier in this letter, in chapter 2 verses 18 and 22, and can be used in the sense of "one pretending to be Christ" (Matthew 24:5) or of "opposing him." One day a great religious leader and a great political leader will together present the two facets of the Antichrist: one looking like a sheep will pretend to be a priest as Christ, supporting the other for worship, who will oppose the true Christ (Revelation 13). Our contemporary civilization is heading for the arrival of the Antichrist:
The spirit of antichrist was in the world since the early days of the church of Christ. He reveals himself in the false teachers who teach heresy and a false gospel.
There is no reason why we who belong to God and not the world should be deceived by antichristian teaching. The Spirit of God that dwells in every believer (Romans 5:5, 8:9), is greater than Satan and his army. He reveals the truth in His word when we seek His guidance, so that we can overcome all the false teaching that we hear. We cannot keep ourselves away from the Bible, be it through ignorance or carelessness, and expect the Spirit of God still to show us the way and guide us. The spirits can only be tested by the Word of God; because it is through the Bible that the Holy Spirit teaches and guides us.
False teachers can be very nice and attractive people, and get an audience with ease. They are in perfect harmony with the world. The occult and the sects grow quickly because they appeal to the flesh. There are Christians who also experiment using the methods of the world to attract a crowd, but they find it difficult to convey the message of the Gospel in this environment. They end up desisting, or silencing over what the world does not want to hear, making the message ineffective.
Unlike the false teachers and the world, we are in tune with the Infinite God. Those who seek God, or want to know Him better, pay attention to our witness, to what we say, to our preaching of the Gospel with all its power, to the teaching in the church, and the faithful ministry in Bible studies.
We need to make sure that the Word of God is being communicated in the power of the Spirit so that the Spirit of God may take it and use it. The people should not come attracted to worldly pleasures, but to hear the Word of God and to come to know the Lord Jesus Christ. The most important thing is to know that Jesus Christ is who He claimed to be and it is that which needs to be clearly announced to the unbelievers.
This is how the spirit of truth is distinguished from the spirit of falsehood.