Theodoret of Cyrus: What We Didn't Know, We Learned from Scripture

Then he brings out also the trustworthiness of the teacher, thus making the teaching more reliable: Knowing from whom you learned it. He reminds him also of his upbringing in piety. And the fact that from a child you have known the sacred writings, which are capable of instructing you for salvation through faith in Christ Jesus (v.15). And since he had borne further witness to the extent of the power in the sacred writings, he emphasizes as well the benefit stemming from them. All Scripture is divinely-inspired and of benefit (v.16). Making a distinction, he set the writings apart from the works of human wisdom, referring to the spiritual Scripture as divinely-inspired: the grace of the divine Spirit spoke through the inspired authors of [the] Old and New Testaments. It follows that the Holy Spirit is God if the Spirit's Scripture is, as the apostle says, divinely-inspired. He brings out also the kinds of benefit. For teaching: what we did not know we learned from there. For censure: it censures our lawless life. For correction: it urges the backsliders to return to the straight and narrow. For training in righteousness: it drills us in the forms of virtue. So that whoever belongs to God may be well-prepared, equipped for every good work (v.17). All these virtues bring perfection and relate us to the God of all.

- 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. 245-46 (2001), Robert C. Hill translator.