Jesus teaches that in this age, the kingdom of God is an abstract reality that cannot be observed. But when he comes back to usher in the kingdom as a tangible reality, it will be as visible as lightning.
The Coming of the Kingdom
In verse 20, Jesus responds to the Pharisees asking when the kingdom of God will come. The KJV gives a literal translation, "The kingdom of God cometh not with observation". In other words, its coming is not something you can see physically. It is something abstract. He does not mention signs (Greek: semeion) at this point. The Pharisees' question was about when the kingdom would come, not about signs.

In verse 21 he continues, "nor will they say, ‘Look, here it is!’ or ‘There!’ For indeed, the kingdom of God is in your midst". Jesus is saying that wherever he is, there the kingdom is. Since the beginning of his ministry, Jesus had been preaching, "Repent, for the kingdom of heaven is near". Although that could be understood as 'near in time', it seems that Jesus meant 'near in proximity'. It was near to them because Jesus was near to them.

The statement here in verse 21b, that the kingdom of God is 'in your midst' is a better translation than 'within you'. The kingdom of God was not within the Pharisees, to whom he was speaking. It was in their midst because Jesus was in their midst. So Jesus' answer to the Pharisees implied that the kingdom had already arrived. However, as Christians, according to John 17:20-23, Jesus lives in us by his Spirit, and we in God. So it would be true to say that the kingdom is 'within us' and that we are 'within the kingdom'.

Although Jesus' kingdom is abstract and unobservable in the present age, there will be many observable signs of his second coming. In the age to come, his kingdom will be observable, tangible, geographic, and political.

The Second Coming
Verses 22 to 37 are part of the Olivet discourse. In Matthew 24 it is all recorded together in one chapter, whereas Luke records part of it here in chapter 17, and the rest in chapter 21.

In verse 22, Jesus implies there would still be a long time before his coming in glory. He refers to his second coming as 'the days of the Son of Man', alluding to Daniel 7:13-14. Daniel saw one like a son of man coming on the clouds in glory. Jesus says his disciples will long to see this, but not see it. During that period of time, which we still live in, there is no point in running after reports that Jesus is 'here' or 'there' (v23). For when he does come, there will be no mistaking it. His coming will be as visible as lightning, from horizon to horizon (v24).

In verse 25, Jesus says he will suffer and 'be rejected by this generation'. In saying this, he implies that he will come back to a future generation. That generation will be like in the days of Noah and of Lot. Both of those generations were especially sinful, and oblivious to their coming destruction (v26-29). Noah's generation was characterised by violence (Genesis 6:13). Lot's generation was characterised by sexual immorality, including homosexuality. Homosexuality was viewed in biblical times as an extreme expression of lust.

In verse 29, Jesus refers to the destruction of Sodom by fire and sulphur which rained down from the sky and destroyed them all. He says that it will be like that on the day the Son of Man is revealed. However, the judgment on Sodom, like the flood in Noah's day, was indiscriminate. Everyone was killed, except for one righteous family in each case. In verse 34, Jesus describes targeted judgments. Two people will be in one bed, but only one taken. Two women will be grinding grain, but only one taken. This is not a description of the rapture. People are 'taken out' in the military sense. It means they are killed. When the disciples ask him where they are taken, he replies, "Where the dead body is, there the vultures will gather". This is a picture of a battlefield scene in which vultures and birds of prey gather to pick the bodies of the slain. It alludes to the prophecy of Egypt's end-time defeat in Ezekiel 32:4, a chapter that also describes the defeat of Antichrist's end-time empire.

In verse 31, Jesus says that on that day, if anyone is on the roof of their house, they should not go down to collect their belongings. In other words, there is no time to delay. They need to flee immediately. It is like the safety instructions when you board an aircraft. The cabin crew tell you that in the event of an emergency you must leave your belongings behind. At this point, Jesus does not specify where they need to flee to, but in Luke 21:21 he tells those in Judea to flee Jerusalem and head for the mountains.

In verse 33, Jesus says, "Whoever tries to keep his life will lose it, but whoever loses his life will preserve it". This implies there will be persecution and martyrdom, and Christians need to be ready to die if necessary rather than deny their faith.

In conclusion, let me summarise the end-time signs that will occur during the end-time generation, according to this chapter:

1) End-time generation characterised by violence (v26) and immorality (v28)
2) End-time generation oblivious to coming judgment (v27-29)
3) Second coming as visible as lighting when it finally happens (v24)
4) People will need to flee without delay when the time comes (v31)
5) Persecution and martyrdom (v33)
6) Vultures gathering, implying great loss of life in end-time judgments (v37)
Symbols: Vultures, Lightning
Tags: Kingdom of God abstract vs tangible, End-time judgments, End-time generation, End-time violence and immorality, Days of Noah, Days of Lot, End-time signs
The Coming of the Kingdom
20 Now at one point the Pharisees asked Jesus when the kingdom of God was coming, so he answered, “The kingdom of God is not coming with signs to be observed,
21 nor will they say, ‘Look, here it is!’ or ‘There!’ For indeed, the kingdom of God is in your midst.”

The Coming of the Son of Man
22 Then he said to the disciples, “The days are coming when you will desire to see one of the days of the Son of Man, and you will not see it.
23 Then people will say to you, ‘Look, there he is!’ or ‘Look, here he is!’ Do not go out or chase after them.
24 For just like the lightning flashes and lights up the sky from one side to the other, so will the Son of Man be in his day.
25 But first he must suffer many things and be rejected by this generation.
26 Just as it was in the days of Noah, so too it will be in the days of the Son of Man.
27 People were eating, they were drinking, they were marrying, they were being given in marriage – right up to the day Noah entered the ark. Then the flood came and destroyed them all.
28 Likewise, just as it was in the days of Lot, people were eating, drinking, buying, selling, planting, building;
29 but on the day Lot went out from Sodom, fire and sulfur rained down from heaven and destroyed them all.
30 It will be the same on the day the Son of Man is revealed.
31 On that day, anyone who is on the roof, with his goods in the house, must not come down to take them away, and likewise the person in the field must not turn back.
32 Remember Lot’s wife!
33 Whoever tries to keep his life will lose it, but whoever loses his life will preserve it.
34 I tell you, in that night there will be two people in one bed; one will be taken and the other left.
35 There will be two women grinding grain together; one will be taken and the other left.”
37 Then the disciples said to him, “Where, Lord?” He replied to them, “Where the dead body is, there the vultures will gather.”