1 John the evangelist, among his fellows and companions the other evangelists, received this special and peculiar gift from the Lord (on whose breast he reclined at the feast, hereby to signify that he was drinking deeper secrets from His inmost heart), to utter those things concerning the Son of God which may perhaps rouse the attentive minds of the little ones, but cannot fill them, as yet not capable of receiving them; while to minds, of somewhat larger growth, and coming to a certain age of inner manhood, he gives in these words something whereby they may both be exercised and fed.
You have heard it when it was read, and you remember how this discourse arose. For yesterday it was read, that “therefore the Jews sought to kill Jesus, because He not only broke the Sabbath, but also said that God was His Father, making Himself equal with God.” This that displeased the Jews, pleased the Father. This, without doubt, pleases them too that honor the Son as they honor the Father; for if it does not please them, they will not be pleasing. For God will not be greater because it pleases you, but you will be less if it displeases you.
Now against this calumny of theirs, coming either of ignorance or of malice, the Lord speaks not at all what they can understand, but that whereby they may be agitated and troubled, and, on being troubled, it may be, seek the Physician. And He uttered what should be written, that it might afterwards be read even by us. Now we have seen what happened in the hearts of the Jews when they heard these words; what happens in ourselves when we hear them, let us more fully consider. For heresies, and certain tenets of perversity, ensnaring souls and hurling them into the deep, have not sprung up except when good Scriptures are not rightly understood, and when that in them which is not rightly understood is rashly and boldly asserted.
And so, dearly beloved, ought we very cautiously to hear those things for the understanding of which we are but little ones, and that, too, with pious heart and with trembling, as it is written, holding this rule of soundness, that we rejoice as in food in that which we have been able to understand, according to the faith with which we are imbued; and what we have not yet been able to understand, that we lay aside doubting, and defer the understanding of it for a time; that is, even if we do not yet know what it is, that still we doubt not in the least that it is good and true.
And as for me, brethren, you must consider who I am that undertake to speak to you, and what I have undertaken: for I have taken upon me to treat of things divine, being a man; of spiritual things, being carnal; of things eternal, being a mortal. Also from me, dearly beloved, far be vain presumption, if my conversation would be sound in the house of God, “which is the Church of the living God, the pillar and foundation of the truth.” In proportion to my measure I take what I put before you: where it is opened, I see with you; where it is shut, I knock with you.
Source: Tractates on the Gospel of John (New Advent)