3 But it seems to me also very absurd to say that the disciples could not then have borne what we find recorded, about things invisible and of profoundest import, in the apostolic epistles, which were written in after days, and of which there is no mention that the Lord uttered them when His visible presence was with them. For why could they not bear then what is now read in their books, and borne by every one, even though not understood? Some things there are, indeed, in the Holy Scriptures which unbelieving men both have no understanding of when they read or hear them, and cannot bear when they are read or heard: as the pagans, that the world was made by Him who was crucified; as the Jews, that He could be the Son of God, who broke up their mode of observing the Sabbath; as the Sabellians, that the Father, and Son, and Holy Spirit are a Trinity; as the Arians, that the Son is equal to the Father, and the Holy Spirit to the Father and Son; as the Photinians, that Christ is not only man like ourselves, but God also, equal to God the Father; as the Manicheans, that Christ Jesus, by whom we must be saved, condescended to be born in the flesh and of the flesh of man: and all others of various perverse sects, who can by no means bear whatever is found in the Holy Scriptures and in the Catholic faith that stands out in opposition to their errors, just as we cannot bear their sacrilegious vaporings and mendacious insanities. For what else is it not to be able to bear, but not to retain in our minds with calmness and composure? But what of all that has been written since our Lord's ascension with canonical truth and authority, is it not read and heard with equanimity by every believer, and catechumen also, before in his baptism he receive the Holy Spirit, even although it is not yet understood as it ought to be? How then, could not the disciples bear any of those things which were written after the Lord's ascension, even though the Holy Spirit was not yet sent to them, when now they are all borne by catechumens prior to their reception of the Holy Spirit? For although the sacramental privileges of believers are not exhibited to them, it does not therefore happen that they cannot bear them; but in order that they may be all the more ardently desired by them, they are honorably concealed from their view.
Source: Tractates on the Gospel of John (New Advent)