36But of that day and hour knoweth no man, no, not the angels of heaven, but my Father only. 37But as the days of Noe were, so shall also the coming of the Son of man be. 38For as in the days that were before the flood they were eating and drinking, marrying and giving in marriage, until the day that Noe entered into the ark, 39And knew not until the flood came, and took them all away; so shall also the coming of the Son of man be. 40Then shall two be in the field; the one shall be taken, and the other left. 41Two women shall be grinding at the mill; the one shall be taken, and the other left.
42Watch therefore: for ye know not what hour your Lord doth come. 43But know this, that if the goodman of the house had known in what watch the thief would come, he would have watched, and would not have suffered his house to be broken up. 44Therefore be ye also ready: for in such an hour as ye think not the Son of man cometh.
45Who then is a faithful and wise servant, whom his lord hath made ruler over his household, to give them meat in due season? 46Blessed is that servant, whom his lord when he cometh shall find so doing. 47Verily I say unto you, That he shall make him ruler over all his goods. 48But and if that evil servant shall say in his heart, My lord delayeth his coming; 49And shall begin to smite his fellowservants, and to eat and drink with the drunken; 50The lord of that servant shall come in a day when he looketh not for him, and in an hour that he is not aware of, 51And shall cut him asunder, and appoint him his portion with the hypocrites: there shall be weeping and gnashing of teeth. (Matthew 24)
What does it mean to be "eating and drinking, marrying and giving in marriage"? Most Christian commentaries interpret this as gluttonous consumption of vittles and some sort of marital excess. The Book of Moses provides more light.
In the pre-flood days of Noah, Noah's granddaughters were taken as wives by "the sons of men," or men who were not of the covenant received by Noah:
8 And Lamech lived one hundred and eighty-two years, and begat a son,
9 And he called his name Noah, saying: This son shall comfort us concerning our work and toil of our hands, because of the ground which the Lord hath cursed....
13 And Noah and his sons hearkened unto the Lord, and gave heed, and they were called the sons of God.
14 And when these men began to multiply on the face of the earth, and daughters were born unto them, the sons of men saw that those daughters were fair, and they took them wives, even as they chose.
15 And the Lord said unto Noah: The daughters of thy sons have sold themselves; for behold mine anger is kindled against the sons of men, for they will not hearken to my voice.
16 And it came to pass that Noah prophesied, and taught the things of God, even as it was in the beginning.
17 And the Lord said unto Noah: My Spirit shall not always strive with man, for he shall know that all flesh shall die; yet his days shall be an hundred and twenty years; and if men do not repent, I will send in the floods upon them. (Moses 8)
20 And it came to pass that Noah called upon the children of men that they should repent; but they hearkened not unto his words;
21 And also, after that they had heard him, they came up before him, saying: Behold, we are the sons of God; have we not taken unto ourselves the daughters of men? And are we not eating and drinking, and marrying and giving in marriage? And our wives bear unto us children, and the same are mighty men, which are like unto men of old, men of great renown. And they hearkened not unto the words of Noah. (Moses 8)
The sons of men cited their having taken wives, eating, drinking, marrying, and giving in marriage as evidence that they were not in need of repentance.
Jesus explains that they were taken by surprise when the flood came, because they were "eating, drinking, marrying and giving in marriage":
38 Now learn a parable of the fig tree—When its branches are yet tender, and it begins to put forth leaves, you know that summer is nigh at hand;
39 So likewise, mine elect, when they shall see all these things, they shall know that he is near, even at the doors;
40 But of that day, and hour, no one knoweth; no, not the angels of God in heaven, but my Father only.
41 But as it was in the days of Noah, so it shall be also at the coming of the Son of Man;
42 For it shall be with them, as it was in the days which were before the flood; for until the day that Noah entered into the ark they were eating and drinking, marrying and giving in marriage;
43 And knew not until the flood came, and took them all away; so shall also the coming of the Son of Man be. (JST Matthew 1)
"Eating, drinking, marrying and giving in marriage" refers to an ordinance of some type practiced in the days of Noah and understood to be of divine origin. I believe it refers to the sacrament (eating and drinking) and plural marriage, but that is merely my belief.
Why does all this matter? Jesus gives us the example of the antediluvian sons of men to warn us of the conditions that will precede his second coming.
Some believe that Jesus' return is a single, point event. This is not the case. Jesus' return is a spectrum of events that begin with the abomination of desolation, continues through all of the destruction events prophesied, and culminates with his return to the Mount of Olives in glory, at which point all those not prepared to dwell in his presence will be destroyed and the millenium ushered in.
In these passages (JST Matthew 1 and Matthew 24), two distinct ideas are discussed: One is what will happen when the Savior returns at the end of the world. The other is what will happen prior to the destruction that precedes the Savior's return.
44 Then shall be fulfilled that which is written, that in the last days, two shall be in the field, the one shall be taken, and the other left;
45 Two shall be grinding at the mill, the one shall be taken, and the other left;
46 And what I say unto one, I say unto all men; watch, therefore, for you know not at what hour your Lord doth come.
47 But know this, if the good man of the house had known in what watch the thief would come, he would have watched, and would not have suffered his house to have been broken up, but would have been ready.
48 Therefore be ye also ready, for in such an hour as ye think not, the Son of Man cometh.
49 Who, then, is a faithful and wise servant, whom his lord hath made ruler over his household, to give them meat in due season?
50 Blessed is that servant whom his lord, when he cometh, shall find so doing; and verily I say unto you, he shall make him ruler over all his goods.
51 But if that evil servant shall say in his heart: My lord delayeth his coming,
52 And shall begin to smite his fellow-servants, and to eat and drink with the drunken,
53 The lord of that servant shall come in a day when he looketh not for him, and in an hour that he is not aware of,
54 And shall cut him asunder, and shall appoint him his portion with the hypocrites; there shall be weeping and gnashing of teeth.
55 And thus cometh the end of the wicked, according to the prophecy of Moses, saying: They shall be cut off from among the people; but the end of the earth is not yet, but by and by. (JST Matthew 1)
Jesus describes that men will be surprised when the destruction is poured out. They will be in the field, in the mill, etc. when some minority of them will "be taken". Many interpret this as some sort of rapture. That is not the case. Instead, the Holy Ghost will inspire a seemingly random subset of the population to gather to places of refuge:
"The righteous disappear, and no man gives it a thought; the godly are gathered out, but no one perceives that from impending calamity the righteous are withdrawn." (Isaiah 57:1, Gileadi Translation)
Jesus says to "watch," as you would if you knew a thief would be coming to rob you. How do we watch? Jesus has told us exactly what will happen: from false teachings and principles being preached to natural disasters to governmental calamities. Are you familiar enough with them to enumerate them? Are you watching for them? Or, do you write off the scriptural warnings of false teachings as applying to some other people or some other time? Do you write off natural disasters as a result of natural causes only (as if God does not work by natural processes, and as if knowing what would happen thousands of years before hand is not as much of a miracle as causing things to occur without scientific explanation)? Do you write off governmental calamities as being just as bad as they ever were? Or, do you see these things as the signs promised in scripture?
Then we get to verses 49-55. Who is the servant whom the Lord made ruler over his house? What is the giving of meat to his house in due season? What would it look like if the ruler was not giving the house meat in due season? What does it mean for the servant to smite his fellow-servants? What personality traits would a servant need to consider himself above his fellow servants, let alone despise them enough to smite them? What does it mean to drink with the drunken? It means to imbibe with the decaying standards and shifting sensibilities of the world. God will cut this servant asunder (interesting connection to the endowment penalties removed in 1990), and appoint his portion with his fellow hypocrites (those that say one thing and do another). This entire passage (49-55) is connected to the antediluvian sons of men who honestly thought they were doing God's will when the flood came upon them because they used some of the same ordinances as the true sons of God.
The watershed moment is when the wicked are cut off from among the people, according to the prophet of Moses. If you don't know what that refers to, you should learn. Go read 3 Nephi 20 and especially 3 Nephi 21.
Some rulers will not be giving the house meat in due season, and will be beating their fellow servants, and forgetting the God they are meant to serve. Others will be giving the house meat, and will be servants to them, and the Lord will find them doing so when he returns.