Bede

Since there are three who bear witness on earth, etc. The Spirit has borne witness that Jesus is truth, when it descended upon Him at His baptism. For if he were not truly the Son of God, by no means would the Holy Spirit have come to Him with such a great manifestation. Water and blood also bore witness that Jesus is truth, when from His side on the cross, after He had died, they flowed out: which could not have happened at all, if He did not have a true nature of flesh. And also this that before His passion, when He prayed, His sweat became like great drops of blood falling to the ground (Luke 22), gives testimony to the truth of the flesh He had assumed. Nor should it be ignored that in this also blood and water bore witness to Him, that from His side after death they flowed out vividly, which was against the nature of dead bodies, and therefore was apt for mysteries, and was fitting as a testimony of the truth, namely showing that the very body of the Lord would live more gloriously after being resurrected, and that His very death would grant us life. This too, that His sweat fell to the ground like drops of blood, bore witness to that holy mystery that He would wash the whole Church all over the world with His blood. Therefore, there are three who bear witness to the truth.

If we accept the testimony of man, the testimony of God is greater, etc. Great is the testimony of man that he gives concerning the Son of God, saying: "The Lord said to my Lord: Sit at my right hand" (Psalm 109). And from the person of the Son himself: "The Lord said to me: You are my Son" (Psalm 2). And likewise from the person of the Father speaking about the Son: "He will call upon me, 'You are my Father, my God, and the rock of my salvation'" (Psalm 88). "My Father," because I am the Son of God. "My God," because I am man. "The rock of my salvation," because I will suffer and be saved from death. "And I (he says) will make him my firstborn, the highest of the kings of the earth" (Ibid.). This is a great and true testimony, worthy of all acceptance. The testimony of man concerning the Son of God is great, but much greater is the testimony of God, who has testified himself about his Son when, speaking from heaven, he said: "You are my beloved Son, in whom I am well pleased" (Luke 3). Great is the testimony of the forerunner, who, bearing testimony about the Son of God, said: "I have baptized you with water, but he will baptize you with the Holy Spirit" (Matthew 3). Greater is the testimony of the Father, who sent the Holy Spirit upon him, whom he was always full of, even visibly.

Whoever does not believe in the Son makes him a liar, etc. In vain the Jews and heretics think they believe in and venerate the Father, as long as they despise Christ and refuse to believe in him. For he who does not honor the Son does not honor the Father who sent him. Those who do not believe in the Son, who says "I and the Father are one" (John 10), and when Caiaphas asked, "Are you the Christ, the Son of the Blessed?" (Mark 14), he replied: "I am" (ibid.); but they argue that he is either not the Christ, or not the Son of God, or not similar to the Father, they certainly make the Father a liar, because they do not believe the testimony he has testified about his Son: namely, in what I mentioned before: "You are my beloved Son, in you I am well pleased" (Luke 3); and even in what he testified when the hour of passion was imminent, while he was praying and saying: "Father, save me from this hour, but for this cause I came to this hour. Father, glorify your name" (John 12), he responded, even the crowd hearing from heaven, "I have both glorified it and will glorify it again" (ibid.), truly signifying himself as God the Father in the heavens of him who, as a true man, was about to suffer death on earth.

And this is the confidence that we have toward him, etc. He provides us with great confidence to hope for heavenly goods from the Lord, because even in this life, whatever we ask of him in a salutary manner, we obtain, according to what he himself promises believers in the Gospel: "I say to you, whatever you ask in prayer, believe that you have received it, and it will be yours" (Mark XI). But it must be noted that we are heard by the Lord when praying in such a way, provided we ask for what he has commanded. He himself says, "Seek first the kingdom of God and his righteousness" (Matthew VI). Hence, John rightly interposed after saying, "Whatever we ask, we receive from him," by adding, "according to his will." Therefore, we are commanded to have full and undoubted confidence of being heard only regarding those things which align not with our own benefits or temporal comforts but with the Lord's will. This is also to be included in the Lord’s Prayer: "Your will be done" (Matthew VI), that is, not ours. For if we remember the Apostle's words: "For we do not know what to pray for as we ought" (Romans VIII), we understand that sometimes we ask for things contrary to our own salvation, and it is most beneficial for us that those things we ask are denied by him who perceives our benefit more rightly than we do. This undoubtedly happened even to the teacher of the Gentiles himself.

There is a sin unto death, etc. A great question arises here, because blessed John clearly shows that there are certain brothers for whom we are not instructed to pray, whereas the Lord even commands us to pray for our persecutors. This can only be resolved by admitting that there are some sins among the brothers which are more grievous than the persecution by enemies. Therefore, the sin of a brother unto death occurs when, after the knowledge of God, which is given through the grace of our Lord Jesus Christ, someone attacks the brotherhood and is inflamed with envy against the very grace by which they were reconciled to God. However, a sin not unto death is if someone has not withdrawn love from their brother but has not shown the duties owed to brotherhood due to some weakness of mind. Therefore, the Lord on the cross says: Father, forgive them, for they do not know what they are doing (Luke 23). For they had not yet become participants in the grace of the Holy Spirit, nor had they entered the communion of holy brotherhood. And blessed Stephen prays for those by whom he was being stoned because they did not yet believe in Christ, nor did they fight against that common grace. And the apostle Paul, for this reason, I believe, does not pray for Alexander because he was already a brother; and he had sinned unto death, that is, by attacking brotherhood with envy. But he prays that those who had not severed love but had succumbed to fear be forgiven. For he thus says: Alexander the coppersmith did me much evil; the Lord will repay him according to his works; whom do you also avoid, for he has greatly resisted our words (2 Tim. 4). Then he adds for whom he prays, saying: At my first defense, no one stood with me, but all forsook me; may it not be charged against them (Ibid.). However, a sin unto death can be understood as one for which someone is forbidden to pray, because a sin that is not corrected in this life, its forgiveness is sought in vain after death. But if we carefully inspect the following, the previous sense of this reading seems to align more with its tenor. For it continues:

All iniquity is sin, etc. Such is the diversity of sins, he says, that everything which deviates from the rule of equity is counted among the sins, although small sins cannot in any way take away or diminish the merit of righteousness from the just, as long as they are those without which this life cannot be lived, and likewise there are certain sins so discordant with all justice, committed with such iniquity, that without any contradiction, unless they are corrected, they lead their perpetrator to eternal punishment. Concerning which it is written: The soul that sins shall die (Ezekiel 18). Blessed John’s statement clearly repudiates the inept argument of the Stoics, who dared to say against all human sense and to affirm that all sins are equal, saying it makes no difference whether a man steals a human being, an ox, or a chicken, because it is not the animal but the intention that constitutes the crime. Jovinian the heretic followed them, asserting that there is no distinction between marriage and virginity, claiming that those who abstain in no way should be preferred in any privilege of recompense over those who simply partake in feasting. Therefore, everything that is unjustly committed or thought is to be referred to as sin. But there are some sins unto death, about which the Apostle says: For those who do such things shall not inherit the kingdom of God (Galatians 5).

We know that we are born of God, etc. We are of God, regenerated by His grace and baptism through faith, and saved so that we may endure in faith. However, the lovers of the world are subjected to the enemy, either never freed from his dominion by the wave of regeneration, or after the grace of regeneration, returned again to his dominion by sinning. Not only the lovers of the world but also those who are recently born and do not yet have discernment of good and evil, because of the guilt of the first violation, belong to the kingdom of the evil enemy unless by the grace of the kind Creator they are rescued from the power of darkness and transferred into the kingdom of the Son of His love (Colossians 1). Hence, he did not simply say that the world is in the evil one but added, And (he says) the whole world is placed in the evil one. For as blessed Ambrose says: "We are all born under sin, whose very birth is in defect." And Pelagius strives in vain to affirm that infants recently born have no need of the grace of baptism to be reborn, because they are said to be born as clean from all stain of sin as Adam was created in paradise, deriving no stain of original guilt from him, and being guilty of nothing until they begin to sin by their own will. But as for us, setting aside the poisons of the Antichrists, which are condemned and expelled from the Church all through this Epistle by the one who drank from the breast of the Lord, the fountain of life, let us hear in the closure the good word of salvation which he pours out for us. Let us observe the works of the supreme King which he tells of. The following ensues: