Tradition
St. Jerome
De Viris Illustribus (Illustrious Men)
Chapter 90
Theodorus, bishop of Heraclea in Thrace, published in the reign of the emperor Constantius commentaries On Matthew and John, On the Epistles and On the Psalter. These are written in a polished and clear style and show an excellent historical sense.
Source: De Viris Illustribus (Illustrious Men) (New Advent)