The interpretation timeline
1 Timothy 4:2 Douay-Rheims

Speaking lies in hypocrisy, and having their conscience seared,

A.D. 202 – 1871 8 witnesses 9 excerpts

Patristic

before A.D. 750
202
A.D.
Irenaeus Patristic
c. A.D. 130–202
“Such are the words and deeds by which, in our own district of the Rhone, they have deluded many women, who have their consciences seared as with a hot iron. Some of them, indeed, make a public confession of their sins; but others of them are ashamed to do this, and in a tacit kind of way, despairing of [attaining to] the life of God, have, some of them, apostatized altogether; while others hesitate between the two courses, and incur that which is implied in the proverb, "neither without nor within;" possessing this as the fruit from the seed of the children of knowledge.”
Source
date
unknown
c. A.D. 380
“If any bishop, or presbyter, or deacon does not on festival days partake of flesh or wine, let him be deprived, as "having a seared conscience," and becoming a cause of scandal to many.”
407
A.D.
John Chrysostom Patristic
A.D. 347–407
“In what way then is she a virgin who has fallen away from the faith, who has devoted herself to the deceivers, who obeys the demons and honors falsehood? In what way is she a virgin who has a seared conscience? For the virgin must be pure not only in body but also in soul if she is going to receive the holy bridegroom.… Virginity is defined by holiness of body and soul. But if a woman is unholy and impure in each respect, how could she be a virgin?… But she shows me a pale face, wasted limbs, a shabby garment and gentle glance.… What is the good of all that when the eye of the soul is bold, for what could be more audacious than that eye encouraging her real eyes to consider the objects of God's creation as bad?”
Source
“"Speaking lies in hypocrisy." This implies that they utter not these falsehoods through ignorance and unknowingly, but as acting a part, knowing the truth, but "having their conscience seared," that is, being men of evil lives. But why does he speak only of these heretics? Christ had before said, "Offenses must need come" (Matt. xviii. 7), and he had predicted the same in his parable of the sower, and of the springing up of the tares. But here admire with me the prophetic gift of Paul, who, before the times in which they were to appear, specifies the time itself. As if he had said, Do not wonder, if, at the commencement of the faith, some endeavor to bring in these pernicious doctrines; since, after it has been established for a length of time, many shall depart from the faith.”
Source

Scholastic

c. 1100 – 1500
1273
A.D.
Thomas Aquinas Catholic
1225–1274
“Above, he instructed Timothy about the things pertaining to the ordering of the Church in spiritual matters; secondly, as to the teaching of the faith, the worship of God, and the disposition of the ministries — here he instructs him about the ordering of the Church as to external things. And first as to foods; secondly as to the states of men and riches, there: whoever are under the yoke. Again, first he treats of the use of foods, secondly of the dispensing of foods, chapter 5, there: honor widows. Again, first he excludes superstitious abstinence; secondly he prefers the piety of lawful abstinence, there: exercise yourself. Again, first he foretells the false doctrine about unlawful abstinence; secondly he instructs him to propose these things to the brothers, there: proposing these things. Again, first he makes the error manifest; secondly he excludes it, there: whom God. Again, first he foretells the error to come on the part of those deceived; secondly on the part of those who deceive, there: in hypocrisy. Again, he sets down the agent of the pronouncement; secondly, the falling-away of faith, there: because in the last; thirdly, the cause of the falling-away, there: giving heed. He says therefore: great is the sacrament of piety, which was justified in the spirit, but beyond this sacrament the Holy Spirit foretells something that is to come. For it belongs to him to reveal mysteries. II Cor. XV, v. 2 and Jn. 16:13: the things that are to come, he will announce to you. The Spirit, therefore, foretells beforehand the future secrets in the heart of the Father. But formerly he spoke in similitudes. Num. 12:6: if there be among you a prophet of the Lord, I will appear to him in a vision, or I will speak to him through a dream. Hos. 12:10: I have multiplied vision, and I have been likened in the hand of the prophets. But in the New Testament the Holy Spirit speaks openly. Jn. 16:25: and openly I will announce to you about my Father. And he foretells the falling-away of faith to come; hence he says in the last times, etc. The last time is called the final age, because we are those upon whom the ends of the ages have come. Yet within this time it is the more the last, the nearer it is to the last day. And just as in the primitive Church, on account of its nearness to Christ and to the sacraments recently instituted, faith was most fervent, so in the last times, in comparison to the time of the apostles, some will depart from the faith, because they will be carnal, but errors will abound the more toward the end. Gen. 49:1: gather together, that I may announce to you the things that are to come to you in the last days, etc. The cause of the falling-away is twofold: one on the part of the Devil who seduces. II Cor. 11:3: I fear lest, as the serpent seduced Eve by his cunning, etc. And therefore he says giving heed to spirits of error, namely to demons, whose office it is to send into error. Jn. 8:44: he is a liar, and the father of it. III Kings, last: I will go forth, and I will be a lying spirit, etc. And he says spirits, because the greater demon has many ministers. But how do they give heed to them? Do they see them? No, but they speak within them. And therefore he adds a second cause, namely false doctrine. And according to the Gloss, he here calls the false teachers demons, and not undeservedly. For just as good men are sometimes called angels, so these, on account of their excelling malice, are called demons. Jn. 6:71: have I not chosen you twelve? And one of you is a devil. On the part of those who deceive there is a twofold cause: one, their falsity; the other, the perversity of their conscience. As to the first he says of demons, that is, of men possessed by a demon, and of these, I say, speaking lies. Jer. 23:26: how long shall this be in the heart of the prophets that prophesy lies, and that prophesy the seductions of their own heart? And note that through a bare lie, without a cloak of appearance, no one could deceive anyone. And so these could deceive no one, unless they put forward some cloak, either of good intention, or of pretense, or of false authority. I Cor. 3:18: let no one seduce you, etc. II Tim. 3:5: having indeed the appearance of piety, that is, feigned piety. And of demons, I say, having their conscience cauterized. A cautery is a corruption in the flesh by fire, from which putrefaction continually issues. So from the fire of a perverse will, of anger, of hatred, of concupiscence, the conscience is ulcerated, and from demons false doctrine issues. Tit. 1:15: their minds are defiled. Then he shows what this false doctrine is, and touches on the heresy of the Manichees, who condemn matrimony, against that word of Matt. 19:6: what God has joined together, let man not separate; I Cor. 7:36: a woman does not sin if she marries. Again, the Manichees forbid the use of foods, that is, they command abstaining from foods. Now one may lawfully abstain from foods with the intention of taming the flesh, as Timothy abstained from wine, or on account of scandal, as the Apostle says, I Cor. 8:13: if food scandalizes my brother, I will not eat meat forever. Again, unlawfully: in one way, on account of the precept of the law, as though the legal observances still had to be kept, against which he speaks in Gal. 2. In another way, according to the heresy of the Manichees, not because it is forbidden by the law (which they condemn), but because they say that in meats, eggs, and wine, and things of this kind, that is, in some particle of such things, the divine nature is mingled — which cannot be thought concerning God. But he does not seem to say this about the foods of the law, because he says in the last days, but about those forbidden by the Manichees. And he calls these Manichees demons, because among all heresies they give more honor to the Devil, because they set him up as a principle equal with the good God, positing him as the principle of visible things. Now the Apostle disproves this erroneous doctrine in two ways: namely from the intention of God who creates foods; secondly from the condition of the creature, there: every creature. He says therefore that they forbid, to abstain, and this is against the intention of God, who created them for receiving. Gen. 9:3: as the green herbs I have given you all things, etc. But you say: are not plants for the sake of animals, and animals for the sake of men? I respond. It must be said that yes, according also to the Philosopher in Politics I, because the imperfect is ordered to the more perfect. And therefore just as in generation there is a manifold perfection — first namely of plants, then of animals, and last the human — so it is in the use of things. And therefore for receiving, but with the giving of thanks. I Thess., last: in all things give thanks; namely because they have been granted to you by God. Ps. 21:26: the poor shall eat, etc. And he adds to the faithful, because those who receive with the giving of thanks are faithful. For no one can give thanks to God in that which is unlawful. For he is foolish who gives thanks to God for fornication, because God is not the author of evils. Therefore he gives thanks who has this, that the use of foods is lawful. And this indeed becomes known through faith alone. And for this reason he says to the faithful. Then when he says who have known the truth, because every, etc., he disproves the error from the condition of the creature. And first he proposes that the creature is good in itself; secondly as to its use. He says therefore every creature is good, namely in its nature. Gen. 1:31: God saw all the things that he had made, and they were very good. From a good author also nothing comes but what is good. But since many things are good in themselves, whose use nevertheless is not good, therefore he proves that every creature is good not only in itself but also as to its use. And first he sets down what is intended, secondly he proves it, there: for it is sanctified. He says therefore nothing is to be rejected, namely by the debt of the divine law, although for another cause: as eating poison, insofar as it is food, is not a sin, but it is to be rejected insofar as it is deadly. Likewise other foods too, insofar as they are such things, are not to be rejected, but insofar as they incite to wantonness. Therefore according to the discretion of reason, and the ordering of charity, they are not to be rejected. Matt. 15:11: everything that enters into the mouth does not defile a man, etc. Why then were certain foods forbidden in the old law? Augustine gives the reason against Faustus, that in that state, Christ was prefigured not only through words, but also through deeds. And therefore in foods, garments, and sacrifices there were figures of the state to come. They are not therefore forbidden in themselves, but because they are figures of unclean things, as the pig is a sign of an unclean life. And therefore the prohibition of its flesh is a sign that in the law of Christ all uncleanness is forbidden. And this is Augustine's example: this word "fatuus" can be considered according as it is a sound composed of letters, and thus it is good; or insofar as it is a sign and signifies such a thing, and thus it is bad and forbidden. Therefore the use of every creature is in itself good. The reason for this is, that if it were evil, this could not be except insofar as the Devil, after the sin of man, had received power over them: because from the moment man sinned, he received power over man, and over the things that are his. But through Christ this power has been taken away, and this is called sanctification. Hence whatever things we bless are first exorcised, and therein is a prayer expelling the Devil. And therefore he says for it is sanctified through the word of God, that is, through Christ, who sanctifies all, Jn. 17:9, and through the prayer of the faithful. Jas.: the persistent prayer of a just man avails much.”

Post-Reformation

c. 1650 – 1900
1832
A.D.
Adam Clarke Methodist
1762–1832
“Speaking lies in hypocrisy - Persons pretending, not only to Divine inspiration, but also to extraordinary degrees of holiness, self-denial, mortification, etc., in order to accredit the lies and false doctrines which they taught. Multitudes of lies were framed concerning miracles wrought by the relics of departed saints, as they were termed. For, even in this country, Thomas a Becket was, deemed a saint, his relics wrought numerous miracles; and his tomb was frequented by multitudes of pilgrims! However, as he works none now, we may rest assured that he never did work any. In 1305, King Edward I. was prevailed on by his clergy to write to Pope Clement V. to canonize Thomas de Cantelupo, bishop of Hereford, because a multitude of miracles had been wrought by his influence; In tantum, says the king, quod ipsius meritis et intercessionibus gloriosis, lumen caecis, surdis auditus, verbum mutis, et gressus claudis, et alia pleraque beneficia ipsius patrocinium implorantibus, caelesti dextra conferuntur. "Insomuch that, by his glorious merits and intercessions, the blind receive their sight, the deaf hear, the dumb speak, and the lame walk; and many other benefits are conferred by the right hand of the Divine Being on those who implore his patronage." And therefore he prays that this dead bishop may be added to the calendar, "that he and his kingdom may enjoy his suffrages and merit his patronage in heaven, who had the benefit of his conversation on earth." Nos attendentes, per Dei gratiam, fideles in Christo, nosque praecipue, et populum regni nostri, ejus posse suffragiis adjuvari, ut, quem familiarem habuimus in terris, mereamur habere patronum in caelis. Foedera, vol. i., p. 976. Edit. 1816. Having their conscience seared with a hot iron - They bear the marks of their hypocrisy as evidently and as indelibly in their conscience in the sight of God, as those who have been cauterized for their crimes do in their bodies in the sight of men. It was customary in ancient times to mark those with a hot iron who had been guilty of great crimes, such as sacrilege, etc. And the heathens supposed that even in the other world they bear such marks; and by these the infernal judges knew the quantum of their vices, and appointed the degrees of their punishment. There is a saying much like that of the apostle in the invective of Claudian against Rufinus, whom he supposes to be thus addressed by Rhadamanthus, one of the infernal judges: - Quid demens manifesta negas? En pectus InUstae Deformant Maculae! vitiisque inolevit imago, Nec sese commissa tegunt. "Thou fool, why dost thou deny what is so manifest? Behold the deep-burnt marks deform thy conscience; the appearance of them has grown up with thy vices; neither can the crimes which thou hast committed hide themselves."”
Source
1849
A.D.
1774–1849
“Their conscience seared; hardened: a metaphor from the custom of burning malefactors with a hot iron. (Witham)”
1863
A.D.
1796–1863
“What they falsely assert, not through ignorance, not as not knowing, but they lie hypocritically, knowing indeed the truth, and having their conscience seared with a hot iron, their lives being wicked." St. Chrysostom.”
1871
A.D.
1871
“Rather translate, "Through (literally, 'in'; the element in which the apostasy has place) the hypocrisy of lying speakers"; this expresses the means through which "some shall (be led to) depart from the faith," namely, the reigned sanctity of the seducers (compare "deceivers," Tit 1:10). having their conscience seared--Greek, "having their own conscience," &c., that is, not only "speaking lies" to others, but also having their own conscience seared. Professing to lead others to holiness, their own conscience is all the while defiled. Bad consciences always have recourse to hypocrisy. As faith and a good conscience are joined (Ti1 1:5); so hypocrisy (that is, unbelief, Mat 24:5, Mat 24:51; compare Luk 12:46) and a bad conscience here. THEODORET explains like English Version, "seared," as implying their extreme insensibility; the effect of cauterizing being to deaden sensation. The Greek, however, primarily means "branded" with the consciousness of crimes committed against their better knowledge and conscience, like so many scars burnt in by a branding iron: Compare Tit 1:15; Tit 3:11, "condemned of himself." They are conscious of the brand within, and yet with a hypocritical show of sanctity, they strive to seduce others. As "a seal" is used in a good sense (Ti2 2:19), so "a brand" in a bad sense. The image is taken from the branding of criminals.”
Source
Modern · 1953 →

The in-app commentary runs from the Fathers to the early-modern record, then stops — that's where the public-domain sources end, not where the reading does. For the modern reading, follow the sources directly.