{Whosoever shall confess} (hos ean homolog(8873)(8869)).
Indefinite relative clause with modal ean (=an) and the first
aorist active subjunctive, "whoever confesses." See  2:23  4:2f. 
for homologe(935c). {That} (hoti). Object clause (indirect
assertion) after homologe(935c). This confession of the deity of
Jesus Christ implies surrender and obedience also, not mere lip
service (cf.  1Co 12:3  Ro 10:6-12 ). This confession is proof
(if genuine) of the fellowship with God ( 1:3f.  3:24 ).