4 Let not then, my brethren, His further words, “As my Father has taught me, I speak these things,” be the occasion of any carnal thought stealing into your minds. For human weakness cannot think, but as it is accustomed to act and to hear. Do not then set before your eyes as it were two men, one the father, the other the son, and the father speaking to the son; as any one of you may do, when you say something to your son, admonishing and instructing him how to speak, to charge his memory with what you have told him, and, having done so, to express it in words, to enunciate distinctly, and convey to the ears of others what he has apprehended with his own.
Think not thus, lest you be fabricating idols in your heart. The human shape, the outlines of human limbs, the form of human flesh, the outward senses, stature and motions of the body, the functions of the tongue, the distinctions of sounds—think not of such as existing in that Trinity, save as they pertain to the servant-form, which the only-begotten Son assumed, when the Word was made flesh to dwell among us. Thereof I forbid you not, human weakness, to think according to your knowledge: nay, rather I require you.
If the faith that is in you be true, think of Christ as such; but as such of the Virgin Mary, not of God the Father. He was an infant, He grew as a man, He walked as a man, He hungered, He thirsted as a man, He slept as a man; at last He suffered as a man, hung on the tree, was slain and buried as a man. In the same form He rose again; in the same, before the eyes of His disciples, He ascended into heaven; in the same will He yet come to judgment. For angel lips have declared in the Gospel, “He shall so come in like manner as you have seen Him go into heaven.” When then you think of the servant-form in Christ, think of a human likeness, if you have faith; but when you think, “In the beginning was the Word, and the Word was with God, and the Word was God,” away with all human fashioning from your heart.
Banish from your thoughts everything bounded by corporeal limits, included in local measurement, or spread out in a mass, how great soever its size. Perish utterly such a figment from your heart. Think, if you can, on the beauty of wisdom, picture to yourself the beauty of righteousness. Has that a shape? A size? A color? It has none of these, and yet it is; for if it were not, it would neither be loved nor worthy of praise, nor be cherished in our heart and life as an object of honor and affection.
But men here become wise; and whence would they so, had wisdom no existence? And further, O man, if you can not see your own wisdom with the eyes of the flesh, nor think of it by the same mental imagery as you can of bodily things, will you dare to thrust the shape of a human body on the wisdom of God?
Source: Tractates on the Gospel of John (New Advent)