Responding to Marcion’s preference for a single Gospel, Irenaeus of Lyon insisted that just one was not enough. And although he knew of several more Gospels of varying worth, he declared that Christians should recognize the authority of no more and no less than four . . . (Jason David BeDuhn, “A Liberal Protestant Perspective on the New Testament Canon,” in Five Views of the New Testament Canon, ed. Stanley E. Peter and Benjamin P. Laird [Grand Rapids, Mich.: Kregel Academic, 2022], 106)
Here is the relevant portion from Against Heresies
8. It is not possible that the Gospels can be either more or fewer in number than they are. For, since there are four zones of the world in which we live, and four principal winds, while the church is scattered throughout all the world, and the “pillar and ground”2 of the church is the gospel and the spirit of life; it is fitting that she should have four pillars, breathing out immortality on every side, and vivifying men afresh. From which fact, it is evident that the Word, the Artificer of all, He that sitteth upon the cherubim, and contains all things, He who was manifested to men, has given us the gospel under four aspects, but bound together by one Spirit. As also David says, when entreating His manifestation, “Thou that sittest between the cherubim, shine forth.” For the cherubim, too, were four-faced, and their faces were images of the dispensation of the Son of God. For, [as the Scripture] says, “The first living creature was like a lion,” symbolizing His effectual working, His leadership, and royal power; the second [living creature] was like a calf, signifying [His] sacrificial and sacerdotal order; but “the third had, as it were, the face as of a man,”—an evident description of His advent as a human being; “the fourth was like a flying eagle,” pointing out the gift of the Spirit hovering with His wings over the church. And therefore the Gospels are in accord with these things, among which Christ Jesus is seated. For that according to John relates His original, effectual, and glorious generation from the Father, thus declaring, “In the beginning was the Word, and the Word was with God, and the Word was God.” Also, “all things were made by Him, and without Him was nothing made.” For this reason, too, is that Gospel full of all confidence, for such is His person. But that according to Luke, taking up [His] priestly character, commenced with Zacharias the priest offering sacrifice to God. For now was made ready the fatted calf, about to be immolated for the finding again of the younger son. Matthew, again, relates His generation as a man, saying, “The book of the generation of Jesus Christ, the son of David, the son of Abraham;” and also, “The birth of Jesus Christ was on this wise.” This, then, is the Gospel of His humanity; for which reason it is, too, that [the character of] a humble and meek man is kept up through the whole Gospel. Mark, on the other hand, commences with [a reference to] the prophetical spirit coming down from on high to men, saying, “The beginning of the gospel of Jesus Christ, as it is written in Esaias the prophet,”—pointing to the winged aspect of the Gospel; and on this account he made a compendious and cursory narrative, for such is the prophetical character. And the Word of God Himself used to converse with the ante-Mosaic patriarchs, in accordance with His divinity and glory; but for those under the law he instituted a sacerdotal and liturgical service. Afterwards, being made man for us, He sent the gift of the celestial Spirit over all the earth, protecting us with His wings. Such, then, as was the course followed by the Son of God, so was also the form of the living creatures; and such as was the form of the living creatures, so was also the character of the Gospel. For the living creatures are quadriform, and the Gospel is quadriform, as is also the course followed by the Lord. For this reason were four principal (καθολικαὶ) covenants given to the human race: one, prior to the deluge, under Adam; the second, that after the deluge, under Noah; the third, the giving of the law, under Moses; the fourth, that which renovates man, and sums up all things in itself by means of the gospel, raising and bearing men upon its wings into the heavenly kingdom.
9. These things being so, all who destroy the form of the gospel are vain, unlearned, and also audacious; those, [I mean,] who represent the aspects of the gospel as being either more in number than as aforesaid, or, on the other hand, fewer. The former class [do so], that they may seem to have discovered more than is of the truth; the latter, that they may set the dispensations of God aside. For Marcion, rejecting the entire gospel, yea rather, cutting himself off from the gospel, boasts that he has part in the [blessings of] the gospel. Others, again (the Montanists), that they may set at nought the gift of the Spirit, which in the latter times has been, by the good pleasure of the Father, poured out upon the human race, do not admit that aspect [of the evangelical dispensation] presented by John’s Gospel, in which the Lord promised that He would send the Paraclete; but set aside at once both the gospel and the prophetic Spirit. Wretched men indeed! who wish to be pseudo-prophets, forsooth, but who set aside the gift of prophecy from the church; acting like those (the Encratitæ)4 who, on account of such as come in hypocrisy, hold themselves aloof from the communion of the brethren. We must conclude, moreover, that these men (the Montanists) cannot admit the Apostle Paul either. For, in his Epistle to the Corinthians, he speaks expressly of prophetical gifts, and recognises men and women prophesying in the church. Sinning, therefore, in all these particulars, against the Spirit of God, they fall into the irremissible sin. But those who are from Valentinus, being, on the other hand, altogether reckless, while they put forth their own compositions, boast that they possess more Gospels than there really are. Indeed, they have arrived at such a pitch of audacity, as to entitle their comparatively recent writing “the Gospel of Truth,” though it agrees in nothing with the Gospels of the Apostles, so that they have really no gospel which is not full of blasphemy. For if what they have published is the Gospel of truth, and yet is totally unlike those which have been handed down to us from the apostles, any who please may learn, as is shown from the Scriptures themselves, that that which has been handed down from the apostles can no longer be reckoned the Gospel of truth. But that these Gospels alone are true and reliable, and admit neither an increase nor diminution of the aforesaid number, I have proved by so many and such [arguments]. For, since God made all things in due proportion and adaptation, it was fit also that the outward aspect of the gospel should be well arranged and harmonized. The opinion of those men, therefore, who handed the gospel down to us, having been investigated, from their very fountainheads, let us proceed also to the remaining apostles, and inquire into their doctrine with regard to God; then, in due course we shall listen to the very words of the Lord. (Against Heresies 3.11.8-9)