There are four gospels and only four, neither more nor less: four like the
points of the compass, four like the chief directions of the wind. The Church, spread all over the world, has in the gospels four pillars and four winds blowing wherever people live.

These four gospels are in actual fact one single Gospel,  a fourfold Gospel inspired by the one Spirit, a Gospel which has four aspects representing the work of the Son of God.

These aspects are like the four cherubs described by Ezekiel. In the prophet's words: `The first had the like ness of a lion,' symbolizing the masterly and kingly role of Christ in priesthood; `the second had the appearance of an ox,' the beast of sacrifice, recalling the perfect sacrifice of Christ; `the third had the face of a man,'  undoubtedly referring to the coming of the Lord in human nature; `and the fourth had the aspect of a flying eagle,' with a clear allusion to the grace of the Spirit hovering over the Church. [cf. Ezek. 1:10; Rev. 4:7]

The four Gospels correspond to these symbols. Christ is at the center of
them.

John actually speaks of his kingly and glorious Sonship to the Father in his opening words: `In the beginning was the Word.' [John 1:1] Luke begins with Zaccharias offering sacrifice. Matthew chooses first of all the Lord's human genealogy. And Mark leads off by calling on the prophetic Spirit which invests humanity from on high.

(Translation by Thomas Spidlik, Drinking from the Hidden Fountain: A Patristic Breviary, Cistercian Publications, Kalamazoo, MI - Spencer, MASS, 1994)