TIMES OF TERROR
The first verse in paraphrase:

You must realize this – that in the last days difficult times will set in.

THE early Church lived in an age when the time was growing late; they expected the second coming at any moment. Christianity developed within Judaism, and it very naturally thought largely in Jewish terms and pictures. Jewish thought had one basic idea. The Jews divided all time into this present age and the age to come. This present age was altogether evil; and the age to come would be the golden age of God. In between, there was the day of the Lord, a day when God would personally intervene and shatter the world in order to remake it. That day of the Lord was to be preceded by a time of terror, when evil would gather itself for its final assault, and the world would be shaken to its moral and physical foundations. It is in terms of these last days that Paul is thinking in this passage.

He says that, in them, difficult times would set in. Difficult is the Greek word chalepos. It is the normal Greek word for difficult, but it has certain usages which explain its meaning here. It is used in Matthew 8:28 to describe the two demoniacs who met Jesus among the tombs. They were violent and dangerous. It is used in Plutarch [Ploo-tahrk] to describe what we would call an ugly wound. It is used by ancient writers on astrology to describe what we would call a threatening conjunction of the heavenly bodies. There is the idea of menace and of danger in this word. In the last days, there would come times which would menace the very existence of the Christian Church and of goodness itself, a final tremendous assault of evil before its ultimate defeat.

Quoted verse:
Matthew 8:28
And when he was come to the other side into the country of the Gergesenes, there met him two possessed with devils, coming out of the tombs, exceeding fierce, so that no man might pass by that way.

In the Jewish pictures of these last terrible times, we get exactly the same kind of picture as we get here. There would come a kind of terrible flowering of evil, when the moral foundations seemed to be shaken. In the Testament of Issachar, one of the books written between the Old and the New Testaments, we get a picture like this:

Know you, therefore, my children, that in the last times
Your sons will forsake singleness
And will cleave unto insatiable desire;
And leaving guilelessness, will draw near to malice;
And forsaking the commandments of the Lord,
They will cleave unto Beliar [Satan].
And leaving husbandry,
They will follow after their own wicked devices,
And they shall be dispersed among the Gentiles,
And shall serve their enemies.
(Testament of Issachar 6:1–2*)

In 2 Baruch, we get an even more vivid picture of the moral chaos of these last times:
And honour shall be turned into shame,
And strength humiliated into contempt,
And probity [integrity and uprightness; honesty] destroyed,
And beauty shall become ugliness . . .
And envy shall rise in those who had not thought aught of themselves,
And passion shall seize him that is peaceful,
And many shall be stirred up in anger to injure many;
And they shall rouse up armies in order to shed blood,
And in the end they shall perish together with them.
(2 Baruch 27**)

In this picture which Paul draws, he is thinking in terms familiar to the Jews. There was to be a final showdown with the forces of evil.

Nowadays, we have to restate these old pictures in modern terms. They were never meant to be anything other than visions; we do violence to Jewish and to early Christian thought if we take them with a crude literalness. But they do enshrine the permanent truth that some time there must come the consummation when evil meets God in head-on collision, and the final triumph of God comes.

*The Testaments of the Twelve Patriarchs [of which the Testament of Issachar is one] is a constituent of the apocryphal scriptures connected with the Bible. It is a pseudepigraphical work [certain writings professing to be Biblical in character.] comprising the dying commands of the twelve sons of Jacob.

**2 Baruch is a Jewish pseudepigraphical text thought to have been written in the late 1st century AD or early 2nd century AD, after the destruction of the Temple in AD 70. It is attributed to the biblical Baruch and so is associated with the Old Testament, but not regarded as scripture by Jews or by most Christian groups. It is included in some editions of the Peshitta, and is part of the Bible in the Syriac Orthodox tradition. It has 87 sections. ~Barclay commentary

Now to the other commentaries.  We will begin with the general and go to the specific.

A Dark Picture of Evil Men

2 Timothy 3:1-9

The last days of the present age are to be black and sorrowful. Sinful rejection of Christ will come to a head. We must not be misled by the wide-spread profession of the forms of religion; this may co-exist with the rankest apostasy. When women are conscious of sins against God, society, and themselves, they are very liable to the seduction of false teachers, who promise peace and condone impurity.

Tares and wheat grow together unto the harvest. The devil has always set himself to counterfeit God’s handiwork: the Holy City by Babylon; the Son of man by the man of sin; blessedness by the worldling’s giddy merriment. Thus the Egyptian conjurers repeated the miracles of Moses by resorting to sleight of hand. So there is a pure gospel and a specious mimicry of it. Wait for the inevitable unfoldings of God’s purpose. Time will show what is true and what is false. In the meantime, examine yourselves whether ye be in the faith. ~The Matthew Henry Main

Now the Matthew Henry Concise that also covers verses 1-9:

Even in gospel times there would be perilous times; on account of persecution from without, still more on account of corruptions within. Men love to gratify their own lusts, more than to please God and do their duty. When every man is eager for what he can get, and anxious to keep what he has, this makes men dangerous to one another. When men do not fear God, they will not regard man. When children are disobedient to their parents, that makes the times perilous. Men are unholy and without the fear of God, because unthankful for the mercies of God. We abuse God's gifts, if we make them the food and fuel of our lusts. Times are perilous also, when parents are without natural affection to children. And when men have no rule over their own spirits, but despise that which is good and to be honoured. God is to be loved above all; but a carnal mind, full of enmity against him, prefers any thing before him, especially carnal pleasure. A form of godliness is very different from the power; from such as are found to be hypocrites, real Christians must withdraw. Such persons have been found within the outward church, in every place, and at all times. There ever have been artful men, who, by pretences and flatteries, creep into the favour and confidence of those who are too easy of belief, ignorant, and fanciful. All must be ever learning to know the Lord; but these follow every new notion, yet never seek the truth as it is in Jesus. Like the Egyptian magicians, these were men of corrupt minds, prejudiced against the truth, and found to be quite without faith. Yet though the spirit of error may be let loose for a time, Satan can deceive the nations and the churches no further, and no longer, than God will permit. ~Matthew Henry Concise

Now notice this from the Biblical Illustrator:

Perilous times
I. The manner of the warning.

“This know also.”

1. It is the duty of ministers to foresee and take notice of the dangers which the churches are falling into.

2. It is the great concern of all professors and believers to have their hearts very much fixed upon present and approaching dangers.

3. Not to be sensible of a present perilous season is that security which the scripture so condemns; and I will leave it with you under these three things—

(1) It is that frame of heart which of all others God doth most detest and abhor. Nothing is more hateful to God than a secure frame in perilous days.
(2) A secure person, in perilous seasons, is assuredly under the power of some predominant lust, whether it appears, or not.
(3) This senseless frame is the certain presage of approaching ruin.

II. The evil itself. “Perilous times”—times of great difficulty, like those of public plagues, when death lies at every door.

III. The manner of introduction—“Shall come.” Our great wisdom then will be to eye the displeasure of God in perilous seasons, since there is a judicial hand of God in them: and we see in ourselves reason enough why they should come.

IV. The time and season of it—“In the last days.” You may take it in what sense you will: the last days, the days of the gospel; the last days towards the consummation of all things; the last days following the days of the profession of churches; and the last days with many of us, with respect to our lives.

1. The first thing that makes a season perilous is, when the profession of true religion is outwardly maintained under a visible predominancy of horrible lusts and wickedness (see 2 Timothy 3 and verse 2, 3, 4. and 5).

(1) Because of the infection.
(2) Because of the effects. When predominant lusts have broken all bounds of Divine light and rule, how long do you think human rules will keep them in order?
(3) Because of the consequences—the judgments of God (2 Thessalonians 2:10-11).

Quoted verse:
2 Thessalonians 2:10-11
10 And with all deceivableness of unrighteousness in them that perish; because they received not the love of the truth, that they might be saved.
11 And for this cause God shall send them strong delusion, that they should believe a lie:

2. A second perilous season is, when men are prone to forsake the truth, and seducers abound to gather them up that are so; and you will have always these things go together. If it be asked, how we may know whether there be a proneness in the minds of men in any season to depart from the truth? there are three ways whereby we may judge of it.

(1) The first is that mentioned in 2 Timothy 4:3 [See Lesson]. When men grow weary of sound doctrine, when it is too plain, too dull, too common, too high, too mysterious, one thing or other that displeases them, and they would hear something new, something that may please.
(2) When men have lost the power of truth in their conversation, and are as prone and ready to part with the profession of it in their minds. Do you see a man retaining the profession of the truth under a worldly conversation? He wants but baits from temptation, or a seducer to take away his faith from him.
(3) The proneness to depart from the truth, is a perilous season, because it is the greatest evidence of the withdrawing of the Spirit of God from His Church.

3. A third thing that makes a perilous season is, professors mixing themselves with the world, and learning their manners. Such a season is dangerous, because the sins of professors in it lie directly contrary to the whole design of the mediation of Christ in this world. Christ “gave Himself for us, that He might purge us from dead works, and purify us unto Himself a peculiar people” (Titus 2:14). “Ye are a royal nation, a peculiar people.”

4. Another perilous season is when there is great attendance on outward duties, but inward, spiritual decays.

5. Times of persecution are also times of peril.

1. Let us all be exhorted to endeavour to get our hearts affected with the perils of the day wherein we live.

(1) Consider the present things, and bring them to rule, and see what God’s Word says of them.
(2) If you would be sensible of present perilous times, take heed of centring in self. Whether you pursue riches, or honours, while you centre there, nothing can make you Sensible of the perils of the day.
(3) Pray that God would give us grace to be sensible of the perils of the day wherein we live.

2. The next thing is this, that there are two things in a perilous season—the sin of it, and the misery of it. Labour to be sensible of the former, or you will never be sensible of the latter.

3. Remember there is a special frame of spirit required in us all in such perilous seasons as these are. And what is that? It is a mourning frame of spirit.

4. Keep up church watch with diligence, and by the rule. When I say rule, I mean the life of it.

5. Reckon upon it, that in such times as these are, all of us will not go free. ~Biblical Illustrator

Now to the specific commentaries. I am going with the Barnes on this one and tell you the verse is in three parts. Others add part 2 and 3.

1] This know also.
2] In the last days.
3] Perilous times shall come.

1] This know also.

This know also - The “object” of this reference to the perilous times which were to occur, was evidently to show the necessity of using every precaution to preserve the purity of the church, from the fact that such sad scenes were to open upon it. The apostle had dwelt upon this subject in his First Epistle to Timothy 2 Tim. 4, but its importance leads him to advert to it again. ~Barnes Notes

This know also - That not only men of bad principles and practices are in the churches now, as before described in the preceding chapter, but that in succeeding ages there would be worse men, if possible, and the times would be still worse; this the apostle had, and delivered by a spirit of prophecy, and informed Timothy, and others of it, that he and they might be prepared for such events, and fortified against them: ~John Gill

2] In the last days.

In the last days - Under the gospel dispensation; some time in that period during which the affairs of the world will be closed up; see the 1 Timothy 4:1 note, and Hebrews 1:2 note. ~Barnes Notes

In the last days - This often means the days of the Messiah, and is sometimes extended in its signification to the destruction of Jerusalem, as this was properly the last days of the Jewish state. But the phrase may mean any future time, whether near or distant. ~Adam Clarke

3] Perilous times shall come.

Perilous times - Grievous, times of distress. ~People's New Testament

Perilous times shall come - Times of danger, of persecution, and of trial. On the general meaning of this passage, and the general characteristics of those times, the reader may consult the 2 Thessalonians 2:1-12 notes, and 1 Timothy 4:1-3 notes [see below]. There can be no doubt that in all these passages the apostle refers to the same events. ~Barnes Notes

That in the last days perilous times shall come - "or hard" and difficult times to live in; not by reason of the outward calamities, as badness of trade, scarcity of provisions, the ravages of the sword, &c. but by reason of the wickedness of men, and that not of the profane world, but of professors of religion; for they are the persons afterwards described, who will make the times they live in difficult to others, to live soberly, righteously, and godly; the days will be evil, because of these evil men: or they will be "troublesome" times, very afflicting and distressing to pious minds; as the places and times, and men and customs of them were to Lot, David, Isaiah, and others: and also "dangerous" ones to the souls of men; who will be beguiled by their fair speeches, and specious pretences, to follow their pernicious ways, which will bring destruction upon them; their doctrines will eat as a gangrene, and their evil communications will corrupt good manners, before observed. And these times will be "in the last days" of the apostolic age, and onward to the end of the world: the Jews generally understand by this phrase, when used in the Old Testament, the days of the Messiah; and which are the last days of the world, in comparison of the times before the law, from Adam to Moses, and under the law, from thence to Christ; and even in the times of the apostles, at least towards the close of them, great numbers of men rose up under the Christian name, to whom the following characters well agree, as the Gnostics, and others; and who paved the way for the man of sin, the Romish antichrist, whose priests and votaries are here likewise described to the life: so that these last days may take in the general defection and apostasy of the church of Rome, as well as those times, which followed the apostles, and those which will usher in the second coming of Christ. The Ethiopic version renders it, "in the latter days will come an evil, or bad year". ~John Gill

Notice some key verses on these perilous times coming.

Daniel 12:7
And I heard the man clothed in linen, which was upon the waters of the river, when he held up his right hand and his left hand unto heaven, and sware by him that liveth for ever that it shall be for a time, times, and an half; and when he shall have accomplished to scatter the power of the holy people, all these things shall be finished.

Daniel 12:11
And from the time that the daily sacrifice shall be taken away, and the abomination that maketh desolate set up, there shall be a thousand two hundred and ninety days.

2 Thessalonians 2:3-12
3 Let no man deceive you by any means: for that day shall not come, except there come a falling away first, and that man of sin be revealed, the son of perdition;
4 Who opposeth and exalteth himself above all that is called God, or that is worshipped; so that he as God sitteth in the temple of God, shewing himself that he is God.
5 Remember ye not, that, when I was yet with you, I told you these things?
6 And now ye know what withholdeth that he might be revealed in his time.
7 For the mystery of iniquity doth already work: only he who now letteth will let, until he be taken out of the way.
8 And then shall that Wicked be revealed, whom the Lord shall consume with the spirit of his mouth, and shall destroy with the brightness of his coming:
9 Even him, whose coming is after the working of Satan with all power and signs and lying wonders,
10 And with all deceivableness of unrighteousness in them that perish; because they received not the love of the truth, that they might be saved.
11 And for this cause God shall send them strong delusion, that they should believe a lie:
12 That they all might be damned who believed not the truth, but had pleasure in unrighteousness.

1 Timothy 4:1-3 [Lesson Verse 1] [Lesson Verse 2] [Lesson Verse 3]
1 Now the Spirit speaketh expressly, that in the latter times some shall depart from the faith, giving heed to seducing spirits, and doctrines of devils;
2 Speaking lies in hypocrisy; having their conscience seared with a hot iron;
3 Forbidding to marry, and commanding to abstain from meats, which God hath created to be received with thanksgiving of them which believe and know the truth.