We are writing these things to you so that our joy [in seeing you included] may be made complete [by having you share in the joy of salvation].

If anyone sees his brother committing a sin that does not lead to death, he will pray and ask [on the believer’s behalf] and God will for him give life to those whose sin is not leading to death. There is a sin that leads to death; I do not say that one should pray for this [kind of sin].

and the Life [an aspect of His being] was manifested, and we have seen [it as eyewitnesses] and testify and declare to you [the Life], the eternal Life who was [already existing] with the Father and was [actually] made visible to us [His followers]—

And the testimony is this: God has given us eternal life [we already possess it], and this life is in His Son [resulting in our spiritual completeness, and eternal companionship with Him].

He who has the Son [by accepting Him as Lord and Savior] has the life [that is eternal]; he who does not have the Son of God [by personal faith] does not have the life.

These things I have written to you who believe in the name of the Son of God [which represents all that Jesus Christ is and does], so that you will know [with settled and absolute knowledge] that you [already] have eternal life.

This is the promise which He Himself promised us—eternal life.