1John 4:1

“All, therefore, are outside of the [Christian] dispensation, who, under pretext of knowledge, understand that Jesus was one, and Christ another, and the Only-begotten another, from whom again is the Word, and that the Saviour is another, whom these disciples of error allege to be a production of those who were made Aeons in a state of degeneracy. Such men are to outward appearance sheep; for they appear to be like us, by what they say in public, repeating the same words as we do; but inwardly they are wolves. Their doctrine is homicidal, conjuring up, as it does, a number of gods, and simulating many Fathers, but lowering and dividing the Son of God in many ways. These are they against whom the Lord has cautioned us beforehand; and His disciple, in his Epistle already mentioned, commands us to avoid them, when he says: "For many deceivers are entered into the world, who confess not that Jesus Christ is come in the flesh. This is a deceiver and an antichrist. Take heed to them, that ye lose not what ye have wrought." And again does he say in the Epistle: "Many false prophets are gone out into the world. Hereby know ye the Spirit of God: Every spirit that confesseth that Jesus Christ is come in the flesh is of God; and every spirit which separates Jesus Christ is not of God, but is of antichrist." These words agree with what was said in the Gospel, that "the Word was made flesh, and dwelt among us." Wherefore he again exclaims in his Epistle, "Every one that believeth that Jesus is the Christ, has been born of God;" knowing Jesus Christ to be one and the same, to whom the gates of heaven were opened, because of His taking upon Him flesh: who shall also come in the same flesh in which He suffered, revealing the glory of the Father.”

“Well, but who is the man of sin, the son of perdition," who must first be revealed before the Lord comes; "who opposeth and exalteth himself above all that is called God, or that is worshipped; who is to sit in the temple of God, and boast himself as being God? " According indeed to our view, he is Antichrist; as it is taught us in both the ancient and the new prophecies, and especially by the Apostle John, who says that "already many false prophets are gone out into the world," the fore-runners of Antichrist, who deny that Christ is come in the flesh, and do not acknowledge Jesus (to be the Christ), meaning in God the Creator.”

“And the apostles, who speak of God, in establishing the truth of the advent of the Lord Jesus Christ, have each of them indicated the appearing of these abominable and ruin-working men, and have openly announced their lawless deeds. First of all Peter, the rock of the faith, whom Christ our God called blessed, the teacher of the Church, the first disciple, he who has the keys of the kingdom, has instructed us to this effect: "Know this first, children, that there shall come in the last days scoffers, walking after their own lusts. And there shall be false teachers among you, who privily shall bring in damnable heresies." After him, John the theologian, and the beloved of Christ, in harmony with him, cries, "The children of the devil are manifest; and even now are there many antichrists; but go not after them. Believe not every spirit, because many false prophets are gone out into the world." And then Jude, the brother of James, speaks in like manner: "In the last times there shall be mockers, walking after their own ungodly lusts. There be they who, without fear, feed themselves." You have observed the concord of the theologians and apostles, and the harmony of their doctrine.”

“Just as in ancient Israel there were some prophets who spoke the word of God and others who did not, so also, as soon as the apostles appeared, speaking in Christ and having the Holy Spirit whom the Lord had given to them, many false apostles were sent by the devil to counterfeit the teaching of the gospel. It is essential to have that gift of the Holy Spirit which is called the discernment of spirits in order to have the ability to test the spirits, to see which ones are to be believed and which ones are to be rejected.”

“"Beloved, believe not every spirit." Because he had said, "In this we know that He abideth in us, by the Spirit which He hath given us." But how this same Spirit is known, mark this: "Beloved, believe not every spirit, but prove the spirits whether they be from God." And who is he that proves the spirits? A hard matter has he put to us, my brethren! It is well for us that he should tell us himself how we are to discern them. He is about to tell us: fear not.”

“The Holy Spirit is spoken of in the Gospel by the name of water; where the Lord "cried and said, If any man thirst, let him come unto me, and drink. He that believeth on me, out of his belly shall flow rivers of living water." But the evangelist has expounded of what He said this: for he goes on to say, "But this spake He of the Spirit, which they that believed on Him should receive." Wherefore did not the Lord baptize many? But what saith he? "For the Holy Ghost was not yet given; because that Jesus was not yet glorified." Then seeing those had baptism, and had not yet received the Holy Ghost, whom on the day of Pentecost the Lord sent from heaven, the glorifying of the Lord was first waited for, so that the Spirit might be given.”

“The water of the sacrament is one thing: another, the water which betokens the Spirit of God. The water of the sacrament is visible: the water of the Spirit invisible. That washes the body, and betokens that which is done in the soul. By this Spirit the soul itself is cleansed and fed. This is the Spirit of God, which heretics and all that cut themselves off from the Church, cannot have. And whosoever do not openly cut themselves off, but by iniquity are cut off, and being within, whirl about as chaff and are not grain; these have not this Spirit.”

“This Spirit is denoted by the Lord under the name of water: and we have heard from this epistle, "Believe not every spirit;" and those words of Solomon bear witness, "From strange water keep thee far." What meaneth, "water"? Spirit. Does water always signify spirit? Not always: but in some places it signifies the Spirit, in some places it signifies baptism, in some places signifies peoples, in some places signifies counsel: thus thou findest it said in a certain place, "Counsel is a fountain of life to them that possess it." So then, in divers places of the Scriptures, the term "water" signifies divers things.”

“First we must scrutinize thoroughly anything that appears in our hearts, as well as anything that is said to us. Has it come purified by the divine and heavenly fire of the Holy Spirit? Or does it lean toward Jewish superstition? Is its surface piety something which has come down from bloated worldly philosophy? We must examine all this most carefully, doing as the apostle bids us.”

“Having explained the teaching on love for one's neighbor, and having pointed to this love as a sign of the abiding of the Spirit whom we have received, the apostle now adds a criterion for distinguishing true brothers and neighbors, so that we, keeping this distinction in mind, might not on account of the commandment of love enter into close relations with false brothers, false apostles, and false prophets, and thereby cause ourselves great harm. For by having fellowship with them as though they were of like mind, we will, first, harm ourselves by fearlessly communicating the teaching of the faith to the impious and casting what is holy before dogs; then we will harm those who are entrusted to us. For our love toward false brothers, false apostles, and false prophets will dispose many to accept them as teachers and to believe their teaching without caution, since they will be led into deception by our association with them. What then is the sign by which they are recognized?”

“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. After John has completed his discourse on love for one's neighbor, and has demonstrated that this is a sign of the permanence of the Spirit we have received, he now adds a judgment concerning those who are truly brothers and neighbors, so that having this, we do not fall into the occasion of the commandment of love concerning false brothers, false apostles, and false prophets, bringing great harm upon ourselves from this. Indeed, by embracing them as if they were of similar character, we will first harm ourselves while we communicate with those who are faithless, and we present holy things to dogs (Matt. 7:6): then, to those who associate with us, our love towards them will persuade many to take them as teachers and to believe what is said by them, while not observing, as if they were stealthily drawn away because of their conduct with us, and what is the indication of these, this is what follows:”