Catena Aurea on John
Prologue
Isaiah 6:1
I saw the Lord sitting on a high and exalted throne; and the house was full of his majesty, and his train filled the temple.
Gloss Isaiah, enlightened by the sublimity of the divine vision, said: "I saw the Lord sitting" etc.
Who is that Lord who is seen, we learn fully in the Evangelist John, who said, Thus said Isaiah, when he saw the glory of God, and spoke of him; no doubt he meant Christ.
Gloss Thus from those words the matter of this Gospel according to John is designated.
Eusebius, Ecclesiastical History Because Matthew and Luke described the birth of the Savior according to the flesh, John was silent about that, and begins with theology and from his divinity. That aspect no doubt was reserved for this outstanding man by the Holy Spirit.
Alcuin Since the Gospel is the summit of all Scripture, John excels among the writers of the gospels in treating the depths of the divine mysteries. He preached the word of God without any writing from the time of the Lord's Ascension for 65 years, until the end of the reign of Domitian. But, after Domitian was killed, with the permission of Nerva, he returned from exile to Ephesus, the bishops of Asia compelled him to write against the heretics about the divinity of Christ which is coeternal with the Father, against the heretics who denied that Christ existed before Mary. Therefore, among the four animals, he is deservedly represented by the flying eagle, which flies higher than all birds, and looks at the sun's rays with unshaken vision.
Augustine, on John John transcends all corners of the earth, all fields of air, all heights of the stars, all choirs and legions of angels. For if he did not transcend all those things which are created, he would not reach Him through whom all things were made.
Augustine, on the Consistency of the Gospels If you carefully observe, you can see that the other three Evangelists concentrated on those temporal deeds and sayings of the Lord which are most important for living the present life well; thus they were concerned with the active life. But John narrated many fewer events of the Lord, but put his energy into writing about his words, especially those that teach about the unity of the Trinity and the happiness of eternal life. Thus the three animals symbolizing the other three Evangelists, i.e., the lion, man, and bull, walk on the earth, because these three Evangelists are most concerned with what Christ did in the flesh, and about the commands which he gave mortal men for right living in this life. John, however, flies like an eagle above the clouds of human weakness, and looks at the light of unchangeable truth with the sharpest and firmest eyes of the heart. For he focused mostly on the divinity of the Lord, in which he is equal to the Father, and in his Gospel he preached that as fully as he thought necessary for people to understand.
Gloss The Evangelist John can say with Isaiah: "I saw the Lord sitting on a high and exalted throne," because by his insight he saw Christ reigning in the majesty of divinity, which is by nature most high and elevated above all else. The Evangelist John also could say: "And the house was full of his majesty", because he tells of Him through whom all things were made, and he says that all men coming into this world are enlightened by his light. He could also say: "His train filled the temple," because he says "The Word became flesh, and we saw his glory as of the onlybegotten of the Father, full of grace and truth, from whose fullness we all received." Thus the preceding words contain the matter of this Gospel. In it John himself points out the Lord sitting on a high throne, when he shows the divinity of Christ. He shows that the earth was filled with his majesty, when he shows that all things were made through his power, and are filled with their own perfections. And he teaches that his train, that is the mysteries of his humanity, fill the temple, that is the Church, when he assures the faithful grace and glory in the sacraments of the humanity of Christ.
Chrysostom, on John If an uneducated barbarian speaks things that no one on earth ever knew, and he alone knows it, that would be a big miracle. But now we have a greater argument than that what is said here is inspired by God, and that is because all hear, and all believe, over all time. Who then would not admire one who has such power?
Origen John means "grace of God", or one who has or has been given grace. Which theologian has ever been given the ability to penetrate the hidden mysteries of the Supreme Good, and teach them to human minds?