Theodoret of Cyrus: Sanctication Defined

This, you see, is God's will, your sanctification (v.3). Then he brings out what kind of virtue he called sanctification. That you abstain from all fornication. There are many forms of licentiousness - hence he did not say fornication, but all fornication.

- Theodoret of Cyrus (around A.D. 393 to around A.D. 457), Commentary on the First Letter to the Thessalonians, Chapter 4, in Theodoret of Cyrus, Commentary on the Letters of St. Paul, Volume 2, p. 115 (2001), Robert C. Hill translator.