Ignatius Theophorus - Epistles to the Churches - c. 107 A.D.

Ignatius of Antioch (/ɪɡˈneɪʃəs/; Greek: Ἰγνάτιος Ἀντιοχείας, Ignátios Antiokheías; died c. 108 also known as Ignatius Theophorus (Ἰγνάτιος ὁ Θεοφόρος, Ignátios ho Theophóros, lit. "the God-bearing")

From Eusebius Church History (Book III):

...Ignatius, who was chosen bishop of Antioch, second in succession to Peter, and whose fame is still celebrated by a great many.
Report says that he was sent from Syria to Rome, and became food for wild beasts on account of his testimony to Christ.
And as he made the journey through Asia under the strictest military surveillance, he fortified the parishes in the various cities where he stopped by oral homilies and exhortations, and warned them above all to be especially on their guard against the heresies that were then beginning to prevail, and exhorted them to hold fast to the tradition of the apostles. Moreover, he thought it necessary to attest that tradition in writing, and to give it a fixed form for the sake of greater security.

So when he came to Smyrna, where Polycarp was, he wrote an epistle to the church of Ephesus, in which he mentions Onesimus, its pastor;
( 00:00:00 - Letter to Ephesus )

and another to the church of Magnesia, situated upon the Mæander, in which he makes mention again of a bishop Damas;
( 00:21:01 - Letter to Magnesia )

and finally one to the church of Tralles, whose bishop, he states, was at that time Polybius.
( 00:32:08 - Letter to Tralles )

In addition to these he wrote also to the church of Rome, entreating them not to secure his release from martyrdom, and thus rob him of his earnest hope. In confirmation of what has been said it is proper to quote briefly from this epistle.
( 00:42:42 - Letter to Rome )

And when he had left Smyrna he wrote again from Troas to the Philadelphians
( 00:54:38 - Letter to Philadelphia )

and to the church of Smyrna;
( 01:04:49 - Letter to Smyrna )

and particularly to Polycarp, who presided over the latter church. And since he knew him well as an apostolic man, he commended to him, like a true and good shepherd, the flock at Antioch, and besought him to care diligently for it.
( 01:17:27 - Letter to Polycarp )