Haydock Catholic Bible Commentary
Know. Do not be troubled at the many evils, persecutions, and heresies, which rise up against the Church. There have ever existed such since the Church was first established, and such ever will exist. Did not Jannes and Mambres rise up against Moses? (Calmet) See 1 Timothy iv. 1.; 2 Peter iii. 3.; Jude 18. --- That in the last days. It only signifies hereafter. And the advice St. Paul give to Timothy, (ver. 5.) now these avoid; shews that some of those false teachers should come in St. Timothy's days. We may observe that few agree exactly in translating or expounding the sense of so many Greek or Latin words, which express the vices of such heretics; but the difference is so small, that it need not be taken notice of. (Witham)
2Ti 3:2 . Cyprian, expounding these words, says: "Let not faithful man, who keepeth in mind our Lord's and apostle's admonition, marvel, if he see in latter times proud and stubborn men, enemies of God's priests, go out of the Church to attack the same, since both our Lord and his apostle have predicted that such things would be."
Having an appearance indeed of piety, in some things, as we may see heretics affect to be thought more exact than the Catholics in some things, by which the devil more easily deceives souls, but denying by their lives the power, virtue, and force of piety. (Witham) --- These avoid. St. Paul having in the preceding verses described the vices and enormities which were to reign in the world in the latter days, here warns Timothy, that already people given to such extravagancies were in the world, and that consequently in regard to Timothy, those days were already come. (St. John Chrysostom, Theophylactus, &c.) --- How many crimes are covered with the cloak of knowledge, and the exterior of piety, and what mischief arises to religion from such base and hypocritical conduct: it cannot be too severely attacked, as we see in Christ's comportment towards the Pharisees.
Of this sort, &c. Here St. Paul gives a true description of heretics, and evil men; such as they have existed in every age. For there never existed a time, either under the Old or New Testaments, in which such have not appeared. Even in the apostle's time, we behold heresies and disorders in the Church. We see them increase rapidly after their decease. Simon, the magician, seems to have been dead when St. Paul wrote this epistle, which was but a short time before his martyrdom. But he had left a great number of disciples behind him, known by the numerous sects, the Gnostics, the Simonians, the Encratians, &c. &c. into which, after the death of their master, they were split. (Calmet) --- Who creep  into houses and lead captive silly  women, &c. That is the custom of almost all heretics. See St. Jerome to Ctesiphon, tom. iv. part 2. p. 477. Nov. edit. where he brings a number of instances, from Simon Magus to his time. (Witham)
Qui penetrant, Greek: endunontes.
Mulierculas, Greek: gunaikaria: nunquam pervenientes, Greek: medapote dunamena, which agrees with Greek: gunaikaria.
Never attaining to the knowledge of the truth. These words, in construction, agree with the aforesaid women. (Witham)
Jannes and Mambres. The names of the magicians, who in Egypt, resisted Moses, says St. John Chrysostom, and though not mentioned in the Scriptures, their names might be known by tradition. (Witham) --- Since the Old Testament does not mention these magicians of Pharao, who opposed Moses, it seems probable that St. Paul either learnt their names by a particular revelation, as St. John Chrysostom, Theophylactus, and Tirinus think, or by some tradition of the Jews, agreeably to the opinions of Theodoret, Grotius, Estius, &c. Others think he might have found their names in some ancient histories, which have not reached our time; or perhaps from the apocryaphal book of Jannes and Mambres, mentioned by Origen and Ambrosiaster. Certain it is, that in St. Paul's time the name of these two famous magicians were very well known; this it is by no means necessary in this instance to have recourse to a particular inspiration. The Orientals say that were many magicians who opposed Moses. Among others, they mention Sabous and Gadous, who came from Thebias; Graath and Mospha, from some other country. They wished, as they inform us, to imitate the miracle by which Moses turned his rod into a serpent, by throwing their canes on the ground, and ropes filled with quicksilver. These ropes began to move a little, one twisting with another, on account of the heat of the earth warmed by the sun. But the rod of Moses in a moment broke them to pieces. (Calmet) --- These magicians are called by different names. The Greek has Jannes and Jambres. Some ancient writers, Jannes and Mambres; as St. Cyprian, Optatus, (chap. 7.) Born. &c. The Jews call that Joanne, or Johanna, whom the Greeks name Jannes; and that called by the Jews Jambres, the Greeks name Mambres. The Hebrews would have them to be the sons of Balaam, the soothsayer, and the masters of Moses in the sciences of the Egyptians. (Calmet)
But they shall proceed no farther. How doth this agree with ver. 13. where it is said, that seducers shall grow worse and worse? or with what he said in the last chapter, (ver. 17.) that their talk spreadeth like a cancer? We may answer, that the heretics became worse, and seduced very many in all ages, but the providence of God always put a stop to their progress, so that they could never prevail against the Church, as they hoped and proposed to do. (Witham) --- St. Paul shews what will be the fate of all heresies; and the annals of the Church prove good his words, that they will appear to flourish for a time, and then will die away and be forgotten.
But continue thou in the things which thou hast learned, &c. St. Paul here gives particular advice to his disciple, St. Timothy, who had been long since instructed in all the truths and mysteries of the Christian faith, who had received the gifts of the Holy Ghost, of prophecy, of interpreting the Scriptures, who was a priest, a bishop of Ephesus, the metropolis of Asia, whose office it was to instruct, direct, and convert others. He tells this great bishop, that the holy Scriptures are able, and may conduce or can instruct him unto salvation, (ver. 15.) unto his own salvation and that of others. (Witham) --- The apostle here entreats his disciple, an din him all future Christians, to adhere to the true deposit of doctrine. He teaches with Catholics, that all Scripture is profitable; but not with Protestants, that Scripture alone is necessary and sufficient.
All scripture divinely inspired is profitable to teach, to reprove, to correct, or admonish, to instruct others in justice, and in the ways of virtue, that thus he who is a man of God, a minister of the gospel, may be perfect and instructed unto every good work. But when our adversaries of the pretended reformation, undertake from these four verses to shew, first, that every ignorant man or woman is hereby warranted to read and put what construction his or her private spirit, or private judgment, suggests upon all places of the holy Scriptures; and secondly, that the Scriptures alone contain all truths which a Christian is bound to believe; or at least, that the Scriptures teach him all things necessary to salvation, without regard to the interpretation and authority of the Catholic Church: I may at least say (without examining at present any other pretended grounds of these assertions) that these consequences are very remote from the text and sense of St. Paul in this place. As to the first, does this follow; the Scriptures must be read by Timothy, a priest, a bishop, a man of God, a minister of the gospel, whose office it is to instruct and convert others, therefore they are proper to be read and expounded by every ignorant man or woman? Does not St. Paul say elsewhere, (2 Corinthians ii. 17.) that many adulterate and corrupt the word of God? does not St. Peter tell us also, (2 Peter iii. 16.) that in St. Paul's epistles are some things....which the unlearned and unstable wrest, as also the other scriptures, to their own perdition? See the preface to [the Gospel of] St. John, where reasons are brought for which it was requisite that the Church should put some restraint to the abuse which the ignorant made of reading the Scriptures in vulgar tongues. As to the second consequence, does it follow: every Scripture divinely inspired is profitable for St. Timothy, for a priest, a bishop, a man of God, a minister and preacher of the gospel, to teach and instruct, and conduce to bring both him and others to salvation; therefore they contain all things that a Christian need to believe? &c. Is not every Christian bound to believe that the books in the canon of the New and Old Testament are of divine authority, as in particular these two epistles of St. Paul to Timothy? Where does the Scripture assure us of this? But of this elsewhere. (Witham) --- Every part of divine Scripture is certainly profitable for all these ends. But if we would have the whole rule of Christian faith and practice, we must not be content with those Scriptures which Timothy knew from his infancy, (that is, with the Old Testament alone) nor yet with the New Testament, without taking along with it the traditions of the apostles and the interpretation of the Church, to which the apostles delivered both the book and the true meaning of it. (Challoner)