And this is the promise which Christ [or, "God"] has given to us: [It is] never ending life. [Note: This passage may mean that God promised us "the Eternal Life," that is, Christ, See John 3:16].

This is [one way] to know we live in [fellowship with] God and that He lives in our hearts: [It is] because He has given us His Holy Spirit [to live within us, See 3:24].

Here is what a complete love will do for us: It will give us boldness in [facing] the judgment day, because the way Jesus acts [regarding love] is the way we should act [while] in this world.

This Jesus is the one whose coming [to earth was introduced] by water [at His immersion. See Matt. 3:13] and [completed] by blood [at His crucifixion, John 19:17-37]. He did not come by the water only, but by the water and by the blood. And it is the Holy Spirit who gives testimony [at both of these events], because the Holy Spirit is [always] the truth. [See John 16:13].

For there are three who give their testimony [about Jesus]:

If anyone [of you] observes his brother [or sister] sinning [in a way that would not lead] to [spiritual] death, he should ask [God, in prayer, to help that person], and God will give him [spiritual] life, [that is], to such ones, provided their sin is not leading to [spiritual] death. There is such a sin that leads to [spiritual] death. [See Heb. 6:4-6; I Tim. 5:6; Heb. 10:26-27; II Pet. 2:20-22]. I am not suggesting that you should ask [God, in prayer] about such a situation.

And [in addition], we know that the Son of God has come [in a physical body, See 4:2] and has given us understanding, so that we can know the True One [i.e., God], and that we are in [fellowship with] the True One, even His Son Jesus Christ. This Son is the true God and eternal life.