The earliest manuscripts we have of major portions of the New Testament are p 45, p 46, p66, and p 75, and they date from 175-250 A. D. The early church fathers (97-180 A.D.) bear witness to even earlier New Testament manuscripts by quoting from all but one of the New Testament books. They are also in the position to authenticate those books, written by the apostles or their close associates, from later books such as the gospel of Thomas that claimed to have been written by the apostles, but were not.
Clement (30-100 A.D.) wrote an epistle to the Corinthian Church around 97 A.D. He reminded them to heed the epistle that Paul had written to them years before. Recall that Clement had labored with Paul (Philippians 4:3). He quoted from the following New Testament books: Luke, Acts, Romans, 1 Corinthians, Ephesians, Titus, 1 and 2 Peter, Hebrews, and James.
The apostolic fathers Ignatius (30-107 A.D.), Polycarp (65-155 A.D.), and Papias (70-155 A.D.) cite verses from every New Testament book except 2 and 3 John. They thereby authenticated nearly the entire New Testament. Both Ignatius and Polycarp were disciples of the apostle John.
Justin Martyr, (110-165 A.D.), cited verses from the following 13 books of the New Testament: Matthew, Mark, Luke, John, Acts, Romans, 1 Corinthians, Galatians, 2 Thessalonians, Hebrews, 1 and 2 Peter, and Revelation.
Irenaeus, (120-202 A.D.), wrote a five volume work Against Heresies in which,
He quoted from every book of the New Testament but 3 John.
He quoted from the New Testament books over 1,200 times.