Luke 17:20-37 records:
"Now when He was asked by the Pharisees when the kingdom of God would come, He answered them and said, 'The kingdom of God does not come with observation; nor will they say, "See here!" or "See there!" For indeed, the kingdom of God is within you.' Then He said to the disciples, 'The days will come when you will desire to see one of the days of the Son of Man, and you will not see it. And they will say to you, "Look here!" or "Look there!" Do not go after them or follow them. For as the lightning that flashes out of one part under heaven shines to the other part under heaven, so also the Son of man will be in His day. But first He must suffer many things and be rejected by this generation. And as it was in the days of Noah, so it will be also in the days of the Son of Man: They ate, they drank, they married wives, they were given in marriage, until the day that Noah entered the ark, and the flood came and destroyed them all. Likewise as it was also in the days of Lot: They ate, they drank, they bought, they sold, they planted, they built; but on the day that Lot went out of Sodom it rained fire and brimstone from heaven and destroyed them all. Even so will it be in the day when the Son of Man is revealed. In that day, he who is on the housetop, and his goods are in the house, let him not come down to take them away. And likewise the one who is in the field, let him not turn back. Remember Lot's wife. Whoever seeks to save his life will lose it, and whoever loses his life will preserve it. I tell you, in that night there will be two men in one bed: the one will be taken and the other will be left. Two women will be grinding together: the one will be taken and the other left. Two men will be in the field: the one will be taken and the other left.' And they answered and said to Him, 'Where, Lord?' So He said to them, 'Wherever the body is, there the eagles will be gathered together.'"
The question the Pharisees ask here is probably intended as a subtle criticism, though we cannot know for certain. It had been more than three years since Jesus first started saying that the kingdom of heaven was at hand. They surely thought that after all this preparation it was past time that the kingdom should commence. They probably doubt that it would ever be established with Jesus as the Messiah. Of course, their desire was for some physical manifestation of God's power that would raise the Jewish nation to supremacy above all others. This was never God's intention, which Jesus explains by first telling them that "the kingdom of God does not come with observation."
"Indeed, the kingdom of God is within you" (Luke 17:21). The word "you" is used here in a general sense and not in reference to the Pharisees specifically. The kingdom that Jesus had said was coming would be a spiritual kingdom (cf. John 18:36; Rom. 14:17). God would not rule the world through the Jewish nation but He would reign in the hearts of His obedient believers. Thus, this spiritual kingdom could not be identified by the observable phenomena of material kingdoms (e.g., earthly kings, worldly thrones, marching armies with weapons of war, lands, etc.). When the kingdom of God was established on the Day of Pentecost in Acts 2, there were 3000 souls who were added to it. However, those who were looking for a physical kingdom didn't realize what had happened that great day in which the gospel plan of salvation was preached for the first time! They didn't observe that the kingdom had come.
Jesus gives further instructions to His disciples on this issue, perhaps privately (cf. Luke 17:22ff).
"The days will come when you will desire to see one of the days of the Son of Man, and you will not see it" - If the Pharisees looked eagerly for a physical Messianic kingdom, then the disciples would be tempted to do something similar in the future; that is, yearn for the Lord Jesus to come again in power and great glory (cf. Titus 2:13; Rev. 22:20). This desire of theirs would especially be strong when they were enduring severe persecution.
However, some foolish disciples, in their restless eagerness, would be tempted to follow the false messiahs who caused much excitement and gathered widespread attention. Jesus warned them not to be deceived by such. When the kingdom of God would at last assume a visible shape at the second coming of Christ, the manifestation would be so glorious, universal, and distinct that it would be absolutely unmistakable. It would be seen by all--like lightning flashing across the sky (cf. Luke 17:24)!
Admittedly, this is a difficult section of Scripture to interpret, especially when compared with Matthew 24 and its parallel passages. However, it seems most likely (in my opinion) that this context (i.e., Luke 17:22-37) is exclusively discussing the second coming of Christ.
Jesus declares that before He comes again in "His day," He must first "suffer many things and be rejected by this generation" (Luke 17:25). This is surely a reference to His crucifixion and to the events that preceded it. Jesus wants this point to be clear so the faith of His disciples will not be weakened by false expectations or misunderstandings.
The way people acted immediately before the flood came is the way people will act immediately before Jesus' second coming (cf. Gen. 7:11-23). How will they act? As they always do! Specifically, they will be feasting, marrying, and enjoying the pleasures of physical life. They will be oblivious to the destruction that is coming down upon them. The same could be said regarding the people of Lot's day immediately before they were destroyed (cf. Gen. 19:15-28; Eze. 16:46-56; Jude 7).
"Even so will it be in the day when the Son of Man is revealed" (Luke 17:30). The world will not be prepared when Jesus returns. His coming will be like a "thief in the night" (I Thess. 5:2; II Pet. 3:10; cf. Matt. 24:44). The world will behave in its usual wicked manner right up until the very end. Of course, then it will be too late to repent--just as it was when the flood came and when the fire and brimstone fell. Everlasting destruction will be the wages of those who don't know God and those who haven't obeyed the gospel (cf. II Thess. 1:6-10; Rom. 6:23).
Admittedly, it seems strange that anyone would be concerned about property on that final day, but such is the teaching of the text (cf. Luke 17:31). If one's love has been centered on earthly things, then he will seek to preserve those things even when such is futile. This was the downfall of Lot's wife. Her turning back did not help her in any way; it only destroyed her. Such will also be the case with those who try to save physical treasure at Jesus' return. Behavior of this sort is certainly an indication of a lack of heavenly treasures (cf. Matt. 6:19-21).
A related verse in Matthew 24:16 (which deals with the destruction of Jerusalem and not the second coming of Christ) differs significantly in that a warning is given to flee to the mountains. Luke does not mention fleeing to the mountains in chapter 17, but he does in Luke 21:21 where he records Jesus' words pertaining to Jerusalem's destruction.
Those who are wise will "remember Lot's wife"(Luke 17:32; cf. Gen. 19:16ff) and not love the world or yearn for it above the fulfillment of God's will (cf. I John 2:15-17).
"Two men in one bed" does not suggest anything perverted whatsoever (Luke 17:34). The word "men" is not in the original text. The meaning here is that there were two people sleeping. Outwardly they were very much alike (as far as what they were doing right then), but inwardly they were obviously very different--one ultimately being saved and the other lost. The same is true in 17:35. "Grinding" is a reference to grain being ground on a stone hand-mill. "Women" is also not in the original text, although the labor described here was generally performed by women. Essentially, there were two people working, and although they appeared to be alike outwardly, inwardly they were very different since one was saved and the other lost.
"One will be taken and the other left" - Jesus repeats this phrase several times in this context. This statement does not support the false doctrine referred to by many as the "Rapture." Jesus is merely making a distinction between the saved and the lost and the order in which they will leave Earth on that final day.
When Jesus comes again "the dead in Christ will rise first" (I Thess. 4:16). Then, those who are faithful and still alive will "be taken" into the clouds to meet the Lord in the air. All of the unfaithful who are still alive or who have been resurrected will then be judged and sentenced to hell. They will not be left on the physical earth (cf. II Pet. 3:10; Matt. 25:31,32).
It should be observed that this context is a reminder that day and night exist simultaneously upon the Earth. When Jesus returns some will be sleeping and others will be working, but they will all see Him when He comes (cf. Rev. 1:7)!
"Where, Lord?" (Luke 17:37). Their question here gave Jesus an opportunity to declare that punishment will not be confined to any one spot; it will ultimately be inflicted wherever sin is found. Sin cries out to God for judgment and retribution as a dead carcass beckons vultures (the text should read "vultures" instead of "eagles"). This principle has always been true. The wickedness of the world in Noah's day led to its destruction. The immorality of Sodom and Gomorrah led to their destruction. The unbelief of the Jews of Christ's day led to the destruction of Jerusalem. The wickedness of men in the last days will lead to the ending of the world at Jesus' return.
Thank you for listening, and may the Lord bless you as you strive to do His will.