Irenaeus was one of the early church fathers, whose writings have been preserved and give us pieces of the history of the early church. This text demonstrates a line of teachers and witnesses that begins with the Apostles and continues through the 2nd century church. In addition, it stands as a good piece of evidence to respond to claims that Christ didn’t exist or that there’s no evidence of him outside the scriptures. Irenaeus knew Polycarp, who the passage describes. Elsewhere Polycarp is connected to the Apostle John. Several epistles from Polycarp still exist.

But Polycarp also was not only instructed by apostles, and conversed with many who had seen Christ, but was also, by apostles in Asia, appointed bishop of the Church in Smyrna, whom I also saw in my early youth, for he tarried [on earth] a very long time, and, when a very old man, gloriously and most nobly suffering martyrdom, departed this life, having always taught the things which he had learned from the apostles, and which the Church has handed down, and which alone are true. To these things all the Asiatic Churches testify, as do also those men who have succeeded Polycarp down to the present time,—a man who was of much greater weight, and a more stedfast witness of truth, than Valentinus, and Marcion, and the rest of the heretics. He it was who, coming to Rome in the time of Anicetus caused many to turn away from the aforesaid heretics to the Church of God, proclaiming that he had received this one and sole truth from the apostles,—that, namely, which is handed down by the Church.

Irenaeus- Ante-Nicene Fathers Volume 1 Chapter 3:6-7

This text was written in the second century. Polycarp was eventually burned at the stake in the colosseum.