Exactly 4 gospels
The church Fathers quote from exactly 4 gospels. Papias (AD 70-160) was a disciple of John and personally knew the daughters of the apostle Philip. He explains how Mark came to author the gospel of Mark documenting the teachings of Peter and how Matthew wrote logia (his gospel) which we can rightly identify as one of the sources for the book of Matthew (the other being Mark). (Eusebius, Ecclesiastical History, 3.39.15).
Ignatius of Antioch (martyred in AD 110) show’s a lot of familiarity with John and alludes to the synoptic gospels. He exhorts the church to follow the ‘decrees’ of the apostles implying that his audience had access to the decrees themselves.
Irenaeus (AD 130-200) declared that “It is not possible that the Gospels can be either more or fewer in number than they are… it is fitting that she should have four pillars…” (Against Heresies, XI, 8).
Justin Martyr (AD 100-165) refers to the gospels as the ‘memoirs’ of the apostles and quotes the gospels when he quotes the memoirs.
For the apostles, in the memoirs composed by them, which are called Gospels, have thus delivered unto us what was enjoined upon them; that Jesus took bread, and when He had given thanks, said, “This do ye in remembrance of Me,148 this is My body;” and that, after the same manner, having taken the cup and given thanks, He said, “This is My blood;” and gave it to them alone. (First Apology, Chapter LXVI quoting Matt 26:27)
He employs a Trinitarian formula and confirms that the memoirs of the apostles are read in the weekly Sunday gathering of the Christians
we bless the Maker of all through His Son Jesus Christ, and through the Holy Ghost. And on the day called Sunday, all who live in cities or in the country gather together to one place, and the memoirs of the apostles or the writings of the prophets are read, as long as time permits (First Apology Chapter LXVII)
and confirms the divinity of Christ.
since we find it recorded in the memoirs of His apostles that He is the Son of God, and since we call Him the Son, we have understood that He proceeded before all creatures from the Father by His power and will (Dialogue with Trypho, Chapter C)
they spake in mockery the words which are recorded in the memoirs of His apostles: ‘He said he was the Son of God: let him come down; let God save him.’ (dialogue with Trypho, Chapter CI quoting Matt 27:42)
he even knows that some of them are not written by the apostles and quotes Luke when referencing the memoirs in this way.
in the memoirs which I say were drawn up by His apostles and those who followed them, [it is recorded] that His sweat fell down like drops of blood while He was praying, and saying, ‘If it be possible, let this cup pass: (Dialogue with Trypho, Chapter CIII quoting Luke 22:44,42)
Justin confirms that the gospel state that Jesus was crucified
And this is recorded to have happened in the memoirs of His apostles. And I have shown that, after His crucifixion, they who crucified Him parted His garments among them. (Dialogue with Trypho, Chapter CIV)
Tatian was a follower of Justin Martyr and he compiled a harmony of the books of Matthew, Mark, Luke, and John. The name of the book was the Diatessaron, which means ‘through the 4’. The name itself conveys a general acceptance which would only raise questions if there was any doubt as to what were the 4.
Finally, Origen (185-254) in his commentary on the book of John confirmed that there are only 4 gospels. Origen (185-254) says:
as learned by tradition about the four gospels, which alone are uncontested in the church of God under heaven, that, first, written was Matthew, once publican but later apostle of Jesus Christ, who published it for the believers from Judaism, composed in Hebrew letters; but second, Mark, who composed as Peter led him, whom he avowed as son in the catholic epistle, saying as follows: “She who is in Babylon, chosen together, sends you greetings and so does my son Mark” and third, Luke, who has composed for those from the Gentiles the gospel praised by Paul; after all of them, John.
From these quotes and citations, we can see that the early Church had not three, five, or 20 gospels but exactly 4. We can identify those 4 as the modern books of Matthew, Mark, Luke, and John.
Early and numerous citations of the New Testament
1st Clement of Rome (AD 30-100) quoted extensively from the NT from between 70-80 AD. He referred to 1 Corinthians 2:9 as Scripture. For [the Scripture] saith, “Eye hath not seen, nor ear heard, neither have entered into the heart of man, the things which He hath prepared for them that wait for Him.” (1st epistle to the Corinthians, Chapter 34. He also extensively cited or alluded to Matthew, Mark, Luke, Acts, Romans, Titus, Hebrews, 2 Corinthians, Galatians, Ephesians, Philemon, Colossians, 1 Timothy, 1 Thessalonians, 1 Peter, 2 Peter, and Revelations.
Likewise Barnabas (AD 80) used the term ‘it is written’ quoting Matt 22:14 signifying that he considers the book Scripture. You can see from the graphic above that Polycarp and Mathetes from the early 2nd century also quoted from much of the NT books. We have such overwhelming support for each book of the NT that we can re-assemble all but 11 verses from quotes in the first 200 years.