Haydock Catholic Bible Commentary
Princes and powers. At the time St. Paul wrote this epistle to Titus, there were many Jews, particularly the disciples of Judas of Gaulan, who maintained that the Hebrews were under no obligation of obeying any other than God, or at most the rulers of their own nation. St. Paul here admonishes them, that in conformity with the example and instruction of our divine Saviour, they ought likewise to obey every other temporal prince set over them by the Almighty, provided they commanded nothing contrary to the law of God. (St. Jerome, Estius, Menochius) --- Piety teaches, and pastors should enforce three duties towards princes: submission to their authority, obedience to their laws, and a disposition of heart to meet all their just desires.
Tit 3:3 may see in this portrait of a child of Adam, drawn by the hand of a master, what we should have been without Jesus Christ, and what we perhaps have been, as often as he has abandoned us to ourselves. Whoever cannot read in this his own depravity, has never studied as he ought his own heart.
The goodness and kindness. Literally, humanity of our Saviour. By humanity  some expound Christ's appearing in his human nature, but by the Greek is meant the love of God towards mankind. (Witham)
Benignitas et humanitas, Greek: chrestotes kai philanthropia. See Estius.
Not by the works, &c. St. Paul in this verse alludes to the sacrament of baptism. This text is brought by divines to prove that baptism, like every other sacrament, produces its effect by its own power, (or, as it is termed in the schools, ex opere operato) independently of any disposition on the part of the receiver. We are saved, says the apostle, not by the works of justice, or any good works we have performed, but our salvation must be attributed solely to the mercy of our Saviour, God, manifested to us by the washing itself of regeneration and renovation of the Holy Ghost. --- by the laver of regeneration, &c. That is, baptism, by which we are born anew the adoptive children of God, by the grace of the Holy Ghost, whom he hath poured, &c. (Witham)
Lavacrum, Greek: loutron. See Ephesians v. 26.
Tit 3:6 presumption of human merits, which have not the grace of Jesus Christ for their principle, is here completely confounded; and the whole glory of our salvation is justly attributed to the mercy of God, through Jesus Christ. A new birth, new creature, new spirit. The effusion of the water upon the body in baptism, is a figure of the salutary effusion of the holy Spirit in the soul to renew it, and to make it a child of God.
Tit 3:7 admirable, and I may say divine adoption, is the sole foundation of a Christian's hope, as the eternal life of the blessed is the sole end of this adoption.
It is a faithful saying. He means what he has already said, of our being justified by the grace and mercy of God. --- And of these things I will have thee to affirm  earnestly. The sense is not, I would herein confirm thee, (as Mr. N. translates, without attention to the Greek, which in so many places shews us the literal sense of the Latin text) but that he would have his disciple, Titus, to confirm and settle others in the belief of these truths, that, as it follows, they may be careful to excel in good works. (Witham)
De his volo te confirmare, Greek: peri touton boulomai se diabebaiousthai: on which St. John Chrysostom says, (Greek: log. st. p. 406.) Greek: toutesti, tauta dialegesthai; I would have to declare these things, &c.
A man that is, &c. Many ancient copies have this passage thus, Avoid a heretic after one reprehension. St. Irenæus, Tertullian, St. Cyprian, St. Ambrose, &c. and many ancient Greek copies, omit a second reprehension. They thought once warning a heretic sufficient; a second correction only served to render him more insolent, and more obstinate in his false opinions. Certainly the faith of Christ has been so firmly established, that a man instructed in Scripture and tradition cannot conscientiously remain a heretic; he must be well aware of the crime of disunion; his own judgment, as St. Paul says, must condemn him.
Knowing that he that is such a one is subverted: a metaphor, from a house that is thrown down, even to the foundation, by the Greek. He speaks of heretics whose obstinacy seems evident, for no one is properly a heretic but who is obstinate in his errors. --- And sinneth, being  condemned; or, condemned by his own judgment, when his ignorance cannot be a sufficient plea for him. (Witham) --- Other offenders are judged and cast out of the Church by the sentence of the pastors of the same Church. Heretics, more unhappy, run out of the Church of their own accord; and by so doing, give judgment and sentence against their own souls. (Challoner)
Proprio judicio condemnatus, Greek: autokatakritos.
Let our men (that is, all Christians) also learn to excel in good and charitable works, by furnishing to others, for necessary uses, according to their wants. (Witham)
Tit 3:15 is no tie so tender or so strong as that of faith and charity. Nothing unites us truly together, but that which unites us all to God and to Jesus Christ, by an union of the same sentiments of faith, the same emotions of love, and the same inclinations of grace.