The time of the bridegroom's return is related to the bridal chamber's construction. When the preparations on the bridal chamber were completed then it would be the proper time. But the groom's father would be the one to give permission. It was a common expression or saying, a Jewish idiom, that a man would say when his friends asked him when his marriage would be. He would reply, "of that day or hour no man knows, but my father only."

The unknown day also is a reference to the Feast of Trumpets, which comes with the observance of the new moon.  Since the new moon has a cycle of 29.5 days, it is uncertain on whether it will be seen comes 29 or 30 days after the last new moon.

Further, since the Feast of Trumpets is also known as the "Wedding of the Messiah", this phrase is a rapture reference in three ways.
1.  It refers to the time in the wedding when the groom would return to fetch his bride,
2.  It refers to the Day of the Feast of Trumpets,
3.  It refers to the "Wedding of the Messiah" on the Feast of Trumpets.

Matthew 24:36 But of that day and hour knoweth no man, no, not the angels of heaven, but my Father only.
Matthew 24:42 Watch therefore: for ye know not what hour your Lord doth come.
Matthew 25:13 Watch therefore, for ye know neither the day nor the hour wherein the Son of man cometh.

Mark 13:32 But of that day and that hour knoweth no man, no, not the angels which are in heaven, neither the Son, but the Father.
Mark 13:33 Take ye heed, watch and pray: for ye know not when the time is.

Luke 12:39 And this know, that if the goodman of the house had known what hour the thief would come, he would have watched, and not have suffered his house to be broken through.

Revelation 3:3 Remember therefore how thou hast received and heard, and hold fast, and repent. If therefore thou shalt not watch, I will come on thee as a thief, and thou shalt not know what hour I will come upon thee.

Note that two of these verses above include mention of the thief, and many of these verses say to watch.  Note also that none of the verses say that no Christian during the end times will ever know, or that we will be in darkness regarding the coming... In fact, the exact opposite is implied by Rev 3:3, namely that if we watch, we should know the time and not be surpised by the thief!  In Luke 12:39, it says if he had known, he would have watched!  Those who believe that Jesus will return on the Feast of Trumpets will really purify themselves annually at that time each year, and re-dedicate their lives to the Lord each time that Fall Festival comes around.

1 John 3:3  And every man that hath this hope in him purifieth himself, even as he is pure.

When the bridal chamber was finished, and the bridegroom's father gave permission, the bridegroom would go to fetch his bride, like a thief in the night. The trumpet would be blown to awaken and alert the bride, so she would be ready.

Some have asked, "sounds like a noisy theif?".  Well, the trumpet was blown for several reasons in scripture.

1.  To gather the people together.  Numbers 10:2-4,7, Jeremiah 4:5, Jeremiah 6:1
2.  To prepare the troops for battle.  Ezekiel 7:14, 1 Corinthians 14:8, Numbers 10:9
3.  To announce the reign of a new king.  1 Kings 1:34, 1 Kings 1:39, 2 Kings 9:13

All of these things are also taking place at the time of the pre tribulation rapture.

1.  The people are gathered together.  2 Thessalonians 2:1, Matthew 24:31, Mark 13:27, as they are gathered together at the Feast of Trumpets, Nehemiah 8, Numbers 10.
2.  God's angels make war on Satan and cast him out at this time.  Rev 12:4,5, Identified as stars & moon darkening in Ezekiel. Ezek 32:7-10, Daniel 8:10, Matt 24:29, Joel 2:31, Rev 8:12, Isa 13:9-11.
3.  Our Lord Jesus Christ begins reigning as king. (married people were also treated as king and queen for a day.)  Zechariah 14:9, Rev 4,5, Dan 7.

God's trumpet voice will also awaken people from the dead.  This awaking trumpet blast is the "last trump" of the rapture. Awaken (resurrection) is a theme of the rapture trumpet. This "last trump" was well known to be speaking of the Feast of Trumpets, the first of the Fall Festivals of the Lord, the time and season of which was well known, one of the themes is to stay awake during Trumpets, also known as "the wedding of the messiah." After the rapture, sudden destruction falls on the world in the seven year tribulation.

What follows is a commentary on the meaning of how 1 Thess 5:1-11 demonstrates in several ways the pre tribulation rapture.  This passage follows the key rapture passage in 1 Thess 4:

1 Thessalonians 4:15 For this we say unto you by the word of the Lord, that we which are alive and remain unto the coming of the Lord shall not prevent them which are asleep.
1 Thessalonians 4:16 For the Lord himself shall descend from heaven with a shout, with the voice of the archangel, and with the trump of God: and the dead in Christ shall rise first:
1 Thessalonians 4:17 Then we which are alive and remain shall be caught up together with them in the clouds, to meet the Lord in the air: and so shall we ever be with the Lord. [caught up=HARPAZO=Rapture]
1 Thessalonians 4:18 Therefore comfort one another with these words.

The Feast of Trumpets is a seasonal festival, like all of the Feasts of the Lord, with a set time.

1 Thess 5:1 But of the times and the seasons, brethren, ye have no need that I write unto you.

1 Thess 5:2 For yourselves know perfectly that the day of the Lord so cometh as a thief in the night.
1 Thess 5:3 For when they shall say, Peace and safety; then sudden destruction cometh upon them, as travail upon a woman with child; and they shall not escape.

The travail upon a woman (birth pangs) is a reference to the seven year tribulation; the time of Jacob's trouble, the "day of the Lord".

[Jer 30:6] Ask ye now, and see whether a man doth travail with child? wherefore do I see every man with his hands on his loins, as a woman in travail, and all faces are turned into paleness?
[Jer 30:7] Alas! for that day is great, so that none is like it: it is even the time of Jacob's trouble, but he shall be saved out of it.

Matthew 24:8 All these are the beginning of sorrows. (KJV)
Matthew 24:8 All these are the beginning of birth pains. (NIV)

Isaiah 13: 6 Howl ye; for the day of the LORD is at hand; it shall come as a destruction from the Almighty.
7 Therefore shall all hands be faint, and every man's heart shall melt:
8 And they shall be afraid: pangs and sorrows shall take hold of them; they shall be in pain as a woman that travaileth: they shall be amazed one at another; their faces shall be as flames.
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The day of the Lord is also known as darkness.

[Amos 5:18] Woe unto you that desire the day of the LORD! to what end is it for you? the day of the LORD is darkness, and not light.
[Amos 5:20] Shall not the day of the LORD be darkness, and not light? even very dark, and no brightness in it?

[John 8:12] Then spake Jesus again unto them, saying, I am the light of the world: he that followeth me shall not walk in darkness, but shall have the light of life.

There are two clear meanings of "ye are not in darkness".  The first is "you have knowledge".  The second is "you will not enter tribulation".

"Children of the light" should know of the times and seasons of the Feast of Trumpets and know about the Wedding of the Messiah, so as to be able to be prepared at the coming of the Lord.  Further they will not enter into the darkness of the Day of the Lord, not enter the darkness of the tribulation.  These two meanings are the subject of the previous verses, so this duel meaning should be clear.

Some have read the phrase "that that day should overtake you as a thief", and said that this means that Jesus will come as a thief on unbelievers.  This notion seems to ignore that the day will come upon everyone!  One difference is that believers, through prophecy, should not be surprised by the thief, while unbelievers will be surprised.  The other difference is that righteous and worthy believers will be in Heaven during the tribulation, so the "Day of the Lord", the darkness of the tribulation, will NOT overtake them or come upon them ever!

Those who would apply the "coming as a thief" to refer to Jesus coming with destruction on the unbelievers, from verses 2 & 3, seem to forget John 10:10, which says Jesus is NOT come to destroy, but to give life abundantly.

John 10:10 The thief cometh not, but for to steal, and to kill, and to destroy: I am come that they might have life, and that they might have it more abundantly.

Our thief, who comes for us at the rapture, comes to give life.

We should always be ready, like a new bride, and not be caught off guard and find ourselves ashamed at the Lord’s coming.

1 John 2:28 And now, little children, abide in him; that, when he shall appear, we may have confidence, and not be ashamed before him at his coming.

1 Thess 5:6 Therefore let us not sleep, as do others; but let us watch and be sober.
1 Thess 5:7 For they that sleep sleep in the night; and they that be drunken are drunken in the night.
1 Thess 5:8 But let us, who are of the day, be sober, putting on the breastplate of faith and love; and for an helmet, the hope of salvation.

Being awakened is a theme in the ten virgins marriage parable. Matt 25:1-13
Mat 25:5 While the bridegroom tarried, they all slumbered and slept.
Mat 25:6 And at midnight there was a cry made, Behold, the bridegroom cometh; go ye out to meet him.
Mat 25:7 Then all those virgins arose, and trimmed their lamps.

Being awakened is a theme of the resurrection, which preceeds the rapture.
Daniel 12:2  And many of them that sleep in the dust of the earth shall awake, some to everlasting life, and some to shame and everlasting contempt.
Ephesians 5:14  Wherefore he saith, Awake thou that sleepest, and arise from the dead, and Christ shall give thee light.

Once again, these verses stress a pre tribulation rapture.

1 Thess 5:9 For God hath not appointed us to wrath, but to obtain salvation by our Lord Jesus Christ,
1 Thess 5:10 Who died for us, that, whether we wake or sleep, we should live together with him.
1 Thess 5:11 Wherefore comfort yourselves together, and edify one another, even as also ye do.

Mat 25:6 And at midnight there was a cry made, Behold, the bridegroom cometh; go ye out to meet him.

1Cor 15:52 In a moment, in the twinkling of an eye, at the last trump: for the trumpet shall sound, and the dead shall be raised incorruptible, and we shall be changed.

1 Thessalonians 4:16 For the Lord himself shall descend from heaven with a shout [command], with the voice of the archangel, and with the trump of God: and the dead in Christ shall rise first:

Revelation 4:1 After this I looked, and, behold, a door was opened in heaven: and the first voice which I heard was as it were of a trumpet talking with me; which said, Come up hither, and I will shew thee things which must be hereafter.

Isaiah 26
16 LORD, in trouble have they visited thee, they poured out a prayer when thy chastening was upon them.
17 Like as a woman with child, that draweth near the time of her delivery, is in pain, and crieth out in her pangs; so have we been in thy sight, O LORD.
18 We have been with child, we have been in pain, we have as it were brought forth wind; we have not wrought any deliverance in the earth; neither have the inhabitants of the world fallen.
19 Thy dead men shall live, together with my dead body shall they arise. Awake and sing, ye that dwell in dust: for thy dew is as the dew of herbs, and the earth shall cast out the dead.
20 Come, my people, enter thou into thy chambers, and shut thy doors about thee: hide thyself as it were for a little moment, until the indignation be overpast.
21 For, behold, the LORD cometh out of his place to punish the inhabitants of the earth for their iniquity: the earth also shall disclose her blood, and shall no more cover her slain.
Isaiah 27:1 In that day the LORD with his sore and great and strong sword shall punish leviathan the piercing serpent, even leviathan that crooked serpent; and he shall slay the dragon that is in the sea.

The Feast of Trumpets was celebrated at Joseph's wedding, which took place "when he went out over the land of Egypt" to gather food during the seven good years for the seven bad years, and to make the Feast of Trumpet (the only new moon festival) a statute and decree in Egypt.

[Pss 81:3] Blow the trumpet at the new moon, at the full moon, on our feast day.
[Pss 81:4] For it is a statute for Israel, an ordinance of the God of Jacob.
[Pss 81:5] He made it a decree in Joseph, when he went out over the land of Egypt. I hear a voice I had not known:

[Gen 41:45] And Pharaoh called Joseph's name Zaphenath-paneah; and he gave him in marriage Asenath, the daughter of Potiphera priest of On. So Joseph went out over the land of Egypt.
[Gen 41:46] Joseph was thirty years old when he entered the service of Pharaoh king of Egypt. And Joseph went out from the presence of Pharaoh, and went through all the land of Egypt.
[Gen 41:47] During the seven plenteous years the earth brought forth abundantly,

What is the voice in Pss 81:5?  1 Thessalonians 4:16 & Rev 4:1 mention a voice along with the trumpet.

It seems most unusual that in Genesis 41:45, two events are described in one verse, the marriage and the Feast of Trumpets decree becoming a law in all of Egypt as Joseph "went out over the land of Egypt".  Imagine your own marriage being mentioned as little more than a footnote!  Actually, this links the Feast of Trumpets to the marriage theme quite strongly.

The seven years of famine is what brings Jacob down into Egypt. Thus, this "seven years of trouble" is the second time period of trouble of seven years in Jacob's life.  The other was the second seven years he had to work for his wife, Rachel.  Once again, the marriage theme comes up.  But these two periods of seven years of trouble in Jacob's life are a double witness that the "time of Jacob's trouble", which is a reference to the tribulation, means that the tribulation will last seven years.

Numbers 10:10 Also in the day of your gladness, and in your solemn days, and in the beginnings of your months, ye shall blow with the trumpets over your burnt offerings, and over the sacrifices of your peace offerings; that they may be to you for a memorial before your God: I am the LORD your God.

Nehemiah 8:
9 And Nehemiah, which is the Tirshatha, and Ezra the priest the scribe, and the Levites that taught the people, said unto all the people, This day is holy unto the LORD your God; mourn not, nor weep. For all the people wept, when they heard the words of the law.
10 Then he said unto them, Go your way, eat the fat, and drink the sweet, and send portions unto them for whom nothing is prepared: for this day is holy unto our LORD: neither be ye sorry; for the joy of the LORD is your strength.
11 So the Levites stilled all the people, saying, Hold your peace, for the day is holy; neither be ye grieved.
12 And all the people went their way to eat, and to drink, and to send portions, and to make great mirth, because they had understood the words that were declared unto them.

Next, we will see a particularly interesting group marriage at an annual feast in Judges 21.