Whosoever shall confess (ος εαν ομολογηση). Indefinite relative clause with modal εαν (=an) and the first aorist active subjunctive, "whoever confesses." See 1. John 2:23; 1. John 4:2 for ομολογεω.

That (οτ). Object clause (indirect assertion) after ομολογεω. This confession of the deity of Jesus Christ implies surrender and obedience also, not mere lip service (cf. 1. Corinthians 12:3; Romans 10:6-12). This confession is proof (if genuine) of the fellowship with God (1. John 1:3; 1. John 3:24).