Whosoever denieth the Son,.... Jesus Christ to be the true, proper, natural, essential, and eternal Son of God:the same hath not the Father; or does not hold the Father; or "believe the Father", as the Syriac version renders it; for there cannot be a father without a son; and he that honours not the Son, by owning him as such, honours not the Father; whatever reflects dishonour on the Son, reflects dishonour on the Father.
If Christ is not truly and properly the Son of God, the Father is not truly and properly the Father of Christ; if Christ is only a Son in a figurative and metaphorical sense, the Father is only a Father in a figurative and metaphorical sense; if Christ is a Son only by office, then the Father is a Father only by office, which is monstrously stupid.