Titus 1:16
They profess—that is, make a profession acknowledging God. He does not deny their theoretical knowledge of God, but that they practically know Him.
deny him—the opposite of the previous "profess" or "confess" Him (I Timothy 5:8; II Timothy 2:12; II Timothy 3:5).
abominable—themselves, though laying so much stress on the contracting of abomination from outward things (compare Leviticus 11:10-13; Romans 2:22).
disobedient—to God (Titus 3:3; Ephesians 2:2; Ephesians 5:6).
reprobate—rejected as worthless when tested (see on Romans 1:28; I Corinthians 9:27; II Timothy 3:8).
