en_tn/1jn/04/15.md

Whoever confesses that Jesus is the Son of God

"Anyone who says the truth about Jesus, that he is the Son of God"

Son of God

This is an important title for Jesus that describes his relationship to God. (See: rc://en/ta/man/jit/guidelines-sonofgodprinciples)

God remains in him and he in God

To remain in someone means to continue to have fellowship with him. See how you translated "remains in God" in 1 John 2:6. Alternate translation: "God continues to have fellowship with him and he continues to have fellowship with God" or "God stays joined to him and he stays joined to God (See: rc://en/ta/man/jit/figs-metaphor)

and he in God

The word "remains" is understood from the previous phrase. Alternate translation: "and he remains in God" (See: Ellipsis)