1 John 2:23

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. Such an one does not hold the true doctrine of the Father, and does not appear to have true faith in him, true love unto him, or real interest in him, only by profession:

[but he that acknowledgeth the Son, hath the Father also]:
this clause is left out in many copies, and stands as a supplement in our version; but is in the Alexandrian copy, in four of Beza's manuscripts, and in some others; and in the Vulgate Latin, Syriac, and Ethiopic versions; and confirms and illustrates what is before said; for as he that denies the sonship of Christ cannot hold the paternity of God, so he that owns the sonship of Christ, the second Person, maintains the paternity of the first; for these two are correlates, and mutually put, or take away each other: no mention is made of the Spirit, because, as yet, no controversy had risen concerning him.