All of the books of the New Testament were already in existence by the beginning of the second century AD. In addition, the four Gospels had already been placed in a collection called “The Gospels” and the Pauline Epistles had already been placed in a collection called “The Apostle.”
The first known list of all twenty-seven books of our New Testament appears in a letter by Athanasius, the Bishop of Alexandria, in 367 AD.
However, long before Athanasius’ letter, Polycarp, a young friend and follower of the Apostle John, quoted from the Gospels of Matthew and John, as well as from ten of Paul’s epistles.
Justin Martyr (150 AD), a contemporary of Polycarp, considered all the Gospels inspired and made mention of most of the books that makeup our present-day Bible.
Irenaeus, who lived around 170 AD, was a disciple of Polycarp who quoted from twenty-three of our New Testament’s twenty-seven books.
Finally, around 200 AD, Clement of Alexandria, recognized almost every book of our New Testament as canonical.