Jamieson, Fausset & Brown, on Titus 1:15

“All things are clean to the clean: but to them that are defiled, and to unbelievers, nothing is clean: but both their mind and their conscience are defiled.”

“all things--external, "are pure" in themselves; the distinction of pure and impure is not in the things, but in the disposition of him who uses them; in opposition to "the commandments of men" (Tit 1:14), which forbade certain things as if impure intrinsically. "To the pure" inwardly, that is, those purified in heart by faith (Act 15:9; Rom 14:20; Ti1 4:3), all outward things are pure; all are open to, their use. Sin alone touches and defiles the soul (Mat 23:26; Luk 11:41). nothing pure--either within or without (Rom 14:23). mind--their mental sense and intelligence. conscience--their moral consciousness of the conformity or discrepancy between their motives and acts on the one hand, and God's law on the other. A conscience and a mind defiled are represented as the source of the errors opposed in the Pastoral Epistles (Ti1 1:19; Ti1 3:9; Ti1 6:5).”

Imported from an open dataset — not yet checked against the printed edition.