John 1:1 In the beginning was the Word, And the Word was with God. And the Word was God.

Saint Thomas Aquinas Catena Aurea in Ioannem Gospel of Saint John

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 isthe summit of all Scriptur, 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 endo 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.