Theodoret of Cyrus: False Teachers Normal and Paul's Sorcerers Source

In the same way that Jannes and Jambres opposed Moses, so too these people oppose the truth, being corrupt in mind and false as far as the faith is concerned (v.8). Weeds normally grow up with grain, he is saying: the preachers of the truth have always had their adversaries. What could be a more famous example of piety than Moses? Yet even he had those men who were sorcerers openly arrayed against the truth. The divine apostle, of course, got their names not from the divine Scripture but from the unwritten tradition of the Jews. It was likely that the grace of the Spirit also revealed them to him.

- Theodoret of Cyrus (around A.D. 393 to around A.D. 457), Commentary on 2 Timothy, Chapter 3, in Theodoret of Cyrus, Commentary on the Letters of St. Paul, Volume 2, p. 244 (2001), Robert C. Hill translator.