John 1:2

These words of the evangelist are a further confirmation and explication of what the evangelist had said before; asserting the eternity of the Son, and his relation to the Father, and oneness of essence with the Father. Whether the evangelist, forewarned by the Spirit of God, did add this repetition to forearm Christians against those errors which did afterward trouble the church, I cannot say; but certain it is, that these words do effectually confute the Eunomians, who distinguished between the Word which in the beginning was with God, and that Word by which all things were made; and the Arians, who make the Father to have existed before the Son; as also the Anomians, who would make the Father and the Son diverse both in nature and will. Some others make this verse a transition to 1 Thessalonians 1:4, and the sense to be, This same was not manifest to the world from the beginning of the world, but was with God until he came to be manifested in the flesh: thus, 1 John 1:2, it is said, he was with the Father, and was manifested unto us. He was manifested in the flesh, 1 Timothy 3:16.