5:1 Everyone who believes [to put your confidence in] that Jesus is the Christ [God’s Messiah] is born of God [refers to spiritual process by which believers receive new life from God and become a part of His family; being born again (cf. Jn. 3:3,7)], and everyone who loves the father [the Heavenly Father is the one who has given us spiritual birth] loves his child [the one to whom the Heavenly Father has given spiritual birth] as well.
5:2 This is how we know that we love [to love as God loves] the children of God: by loving God and carrying out his commands [including the directive that we love God’s children (1 Jn. 3:23; 4:21)].
5:3 This is love for God: to obey [the indwelling Spirit enablers believers to keep His commands] his commands [cf. Jn. 14:15,21,23-24,31; 15:10]. And his commands are not burdensome [cf. Matt. 11:28-30],
5:4 for everyone born of God overcomes [conquer, defeat] the world [refers to people antagonistic to God’s family (the church); sinful humanity which is alienated from God]. This is the victory [Gr. “nike” (like the sports shoes)] that has overcome the world [the world system that opposes God], even our faith.
5:5 Who is it that overcomes [to conquer the disbelief and hatred of the world] the world? Only he who believes that Jesus is the Son of God.
5:6 This is the one who came by water and blood—Jesus Christ. He did not come by water only, but by water and blood. And it is the Spirit who testifies, because the Spirit is the truth.
5:7 For there are three that testify:
5:8 the Spirit, the water and the blood; and the three are in agreement.
5:9 We accept man’s testimony, but God’s testimony [in essence, the Bible contains His testimonies to His Son] is greater because it is the testimony of God, which he has given about his Son.
5:10 Anyone who believes in the Son of God has this testimony in his heart [because the indwelling Holy Spirit bears witness]. Anyone who does not believe God has made him out to be a liar [by their unbelief unbelievers are saying that God lied and does not give eternal life through Christ], because he has not believed the testimony God has given about his Son.
5:11 And this is the testimony:  God has given us eternal life [eternal life begins when a person trusts Jesus as Savior, and it never ends], and  this life is in his Son [likely that John was addressing a heresy that said that eternal life can be attained without a relationship with God through Christ].
5:12 He who has the Son has life; he who does not have the Son of God does not have life.
5:13 I write [cf. Jn. 20:31] these things [refers to John’s main reason for writing his epistle] to you who believe in the name of the Son of God [absolute reliance on Christ for salvation] so that you may know [false teachers caused believers to doubt whether they really possessed eternal life] that you have eternal life.
5:14 This is the confidence we have in approaching God: that if we ask anything according to his will, he hears us.
5:15 And if we know that he hears us—whatever we ask—we know that we have what we asked of him.
5:16 If anyone sees his brother commit a sin that does not lead to death, he should pray and God will give him life. I refer to those whose sin does not lead to death. There is a sin that leads to death. I am not saying that he should pray about that.
5:17 All wrongdoing is sin, and there is sin that does not lead to death.
5:18 We know that anyone born of God does not continue to sin [describes a lifestyle, not a single act]; the one [God’s own Son] who was born of God keeps him safe, and the evil one cannot harm [to touch or strike with the result of harming or destroying] him.
5:19 [cf. Col. 1:13] We know [certainty based on trustworthy evidence (testimony)] that we are children of God, and that the whole world is under the control of the evil one.
5:20 We know also that the Son of God has come and has given us understanding, so that we may know him who is true. And we are in him who is true—even in his Son Jesus Christ. He is the true God and eternal life.
5:21 Dear children, keep yourselves from idols.