John states in 5:13 that he wrote “these things” (anaphoric looking back to the entire letter) that the believers may know that they do have eternal life. The purpose statement in the Gospel of John was “But these are written that you may believe that Jesus is the Christ, the Son of God, and that by believing you may have life in his name” (20:31). See John 1:12 (But to all who have received him – those who believe in his name – he has given the right to become God’s children) and John 3:18 (The one who believes in him is not condemned. The one who does not believe has been condemned already, because he has not believed in the name of the one and only Son of God) for similar language. The term “knowing” occurs six times in 5:13-21 which shows us that assurance is the emphasis here.
The presence of the “and” in the beginning of 5:14 sentence “suggests that the author wants to say that, along with assurance of eternal life, believers also experience confidence in their relationship with God and, in particular, confidence in prayer” (Kruse, 189). In the Gospel of John we have similar wording in 1:1 concerning the Word. This verse here also resembles the Lord’s teaching found in John 16:23-26. Confidence in prayer has been talked about already in 1 John 3:22-23; there the author “linked confidence in prayer to pleasing God by doing what he commanded (believing in the name of his Son and loving fellow believers)” (Kruse, 189-90). Schnackenburg writes: “We cannot fail to notice how certain the Johannine Christ is of being heard by his Father (John 11:41f.). This provides the supreme example of the power of prayer. Christians share in this power to the same degree or distance that their own fellowship with God approximates to the intimacy of the Father and the Son or fails to do so” (The Johannine Epistles, 248 quoted in Kruse, 190 n 221).
John is certain that God hears our prayers and answers them!
Starting in 5:16 we see a slight shift in emphasis. John now writes concerning a brother who sins (or: commits a sin). There are many issues in this verse in which we will not have the time to go into, yet the following should be said. Prayer is powerful and John expects us to pray for one another. We should pray for one another so that we might enjoy the Christian life to the fullest. Whatever the sin is that leads to death (see post on 1 John 3:4-10) we are to take care of one another.
The NET footnote to 5:17 reads:
“The meaning of ἀδικία (adikia) here is ‘unrighteousness’ (BDAG 20 s.v. 2). It refers to the opposite of that which is δίκαιος (dikaios, ‘right, just, righteous’) which is used by the author to describe both God and Jesus Christ (1 John 1:9; 2:2, 29). Here, having implied that sins committed by believers (sins ‘not to death’) may be prayed for and forgiven, the author does not want to leave the impression that such sin is insignificant, because this could be viewed as a concession to the views of the opponents (who as moral indifferentists have downplayed the significance of sin in the Christian’s life).”
If the phrase “he who was born of God” (ὁ γεννηθεὶς ἐκ τοῦ θεοῦ) in 5:18 is referring to Christ, we have here the only occurrence in Johannine literature to speak of Jesus being born of God; see the parallel to John 17:12-15. That the world is under the power of the evil one (5:19) is also seen in the Gospel of John (John 12:31; 14:30; 16:11). In 1 John 2:18–19; 4:1–5 we saw that the secessionist are those who are of this world.
Concerning 5:20 Schnackenburg writes: “For here the full identity of Jesus with God is recognized without reserve (note the article with theos, God). This seems to occur intentionally at the end of the letter, at the climax of the triumphant expression of faith. It is hardly an accident that it is precisely at the beginning (1:1, 18) and the end (20:28) of the Gospel of John that the light of Jesus’ divinity shines forth most fully. The climactic christological confession becomes visible here in all its clarity” (The Johannine Epistles, 263; quotes in Kruse 197). “The general concept of believers dwelling in God/in his Son is found in nine other passages in the letter (2:5, 6, 24, 28; 3:6, 24; 4:13, 15, 16). Sometimes it is part of a broader concept: the mutual indwelling of believers in God and God in believers (3:24; 4:13, 15, 16)” (Kruse, 196).
What a tremendous privilege it is to be called sons and daughters of God. We live under the New Covenant in which God circumcises our hearts and His Spirits indwells us and empowers us to live a life pleasing to God.
The abrupt ending of 5:21 seems a bit obscure, yet Brown (627-28) writes: “In speaking of joining the secession and accepting its theology as ‘going after idols’, the author would have been intelligible to a Christian community whose language and thought had Jewish parallels — a background we have found in both the Gospel of John and 1 John.” Though there are many other explanation put forward “the immediate context [makes clear that] keeping oneself from idols is the necessary concomitant of knowing the true God through Jesus Christ” (Kruse, 202).