Jerusalem, on Mount Zion, signifies the doctrine of love to the Lord, and how it governs your life. Jerusalem first comes to our attention in 2 Samuel 5, when King David takes the city from the Jebusites and makes it his capital. In the next chapter he brings the Ark of the Covenant there, and later it is where Solomon builds the temple, and his own palace. From then on Jerusalem is the center of worship of the Israelitish church. It is the place where the Lord was presented in the temple as a baby, where He tarried to talk to the priests at age twelve, where He cleansed the temple, had the last supper, was crucified and then rose. It is a central place in both the old and new Testaments. The city was built on Mount Zion, the highest point of the mountains of Judea. A city, in the Word, represents doctrine, the organized knowledge of the truths of the church. Mountains represent love of the Lord and the consequent worship. If you put those things together, Jerusalem on Mount Zion signifies the doctrine of love to the Lord, and how it governs your life. This is why David was led to make Jerusalem the most important city of the land, and why all worship was conducted there. And this is also why Jeroboam was condemned for introducing idol worship in Samaria. In the Book of Revelation, John's vision of the city New Jerusalem descending from God is a prophecy of a new dispensation of doctrine coming from the Lord.

(Referenties: Arcana Coelestia 4539, 8938; The Apocalypse Explained 365 [35-38])

4334. But of that day and hour no one knows means that the state of the Church at that time so far as forms of good and truth are concerned is not going to be visible to anyone either on earth or in heaven, for 'day' and 'hour' in this case are not used to mean day and hour, that is, a period of time, but a state so far as good and truth are concerned. Periods of time in the Word mean states, see 2625, 2788, 2837, 3254, 3356, and 'day' also has the same meaning, 23, 487, 488, 493, 893, 2788, 3462, 3785. 'Hour,' too therefore is descriptive of state, but some specific aspect. The reason why state so far as good and truth are concerned is meant is that the subject is the Church, for good and truth constitute the Church.

[2] Not even the angels of heaven, but My Father only means that heaven does not know the specific nature of the state of the Church so far as good and truth are concerned; the Lord alone knows. Nor does it know when that state of the Church is going to be reached. The Lord Himself is meant by 'the Father', see 15, 1729, 2004, 2005, 3690; also the Divine Good within the Lord is called 'the Father' and the Divine Truth originating in Divine Good is called 'the Son', see 2803, 3703, 3704, 3736. People therefore who believe that the Father is one and the Son another, and who keep the two apart, do not understand the Scriptures.

[3] But as they were in the days before the Flood means the state of vastation undergone by those who belonged to the Church. This state is compared to the state of vastation which the first or Most Ancient Church underwent, the close of their age, that is, their last judgement, being described in the Word by means of the Flood. For 'the Flood' means a deluge of evils and falsities and the close of that age which followed as a result, see 310, 660, 662, 705, 739, 790, 805, 1120; and 'days' means states, see above.

[4] Eating and drinking, marrying and giving in marriage means their state insofar as they made evil and falsity their own, and by doing this became joined to these. For 'eating' means making good one's own, and 'drinking' making truth one's own, see 3168, 3513 (end), 3596; and so in the contrary sense they mean making evil and falsity one's own. 'Marrying' means becoming joined to evil and 'giving in marriage' becoming joined to falsity, as may be seen from what has been stated and shown about marriage and conjugial love in 686, 2173, 2618, 2728, 2729, 2737-2739, 2803, 3132, 3155, to the effect that in the internal sense the joining together of good and truth is meant by them, though here in the contrary sense the joining together of evil and falsity is meant. Everything the Lord has said, since it is Divine, is of a different nature in the internal sense from what it is in the letter. So eating and drinking in the Holy Supper do not in the spiritual sense mean eating and drinking but making the good of the Lord's Divine love one's own, 2165, 2177, 2187, 2343, 2359, 3464, 3478, 3735, 4211, 4217. And as the joining of good which is the good of love to truth which is the truth of faith is meant when the idea of a marriage is used in reference to the Church or to the Lord's kingdom, so therefore is the Lord's kingdom in the Word called the heavenly marriage.

[5] Up to the day on which Noah entered the ark means the end of the former Church and the beginning of the new one, for 'Noah' means the Ancient Church in general which replaced the Most Ancient after the Flood, 773 and elsewhere, while 'the ark' means the Church itself, 639. The word 'day' which is used several times in these verses means state, as shown just above.

[6] And they were unaware of anything until the flood came and took them all away means that members of the Church at that time will not know that they have been swamped by evils and falsities because, on account of the evils and falsities in which they are immersed, they will have no knowledge of what the good of love to the Lord is and what the good of charity towards the neighbour is, nor also what the truth of faith is. Nor will they know that such truth originates in those forms of good and that it cannot exist except with people who lead lives filled with such love and charity, in addition to which they will have no knowledge of the fact that what is internal saves or condemns, not what is external separated from internal.

[7] So also will be the coming of the Son of Man means Divine Truth which they will not entertain. The meaning of 'the coming of the Son of Man' as Divine Truth which will be revealed at that time has been discussed already at verses 27-30, and in 2803, 2813, 3704, as well as 3004-3006, 3008, 3009.

[8] At that time two will be in the field; one will be taken and one will be left behind means those within the Church who are governed by good and those within the Church who are governed by evil; the former will be saved and the latter condemned. For 'the field' means the Church as regards good, see 2971, 3196, 3310, 3317, 3766.

[9] Two women grinding at the mill; one will be taken and one will be left behind means the future salvation of those within the Church who know the truth, that is, who are led by good to have an affection for it, and the future condemnation of those within the Church who know the truth, but who are led by evil to have an affection for it. These meanings which 'grinding' and 'mill' have in the Word will be clear from what appears immediately below.

From all this it is now evident that the words under consideration describe what the state of good and truth will be like within the Church when that Church is set aside and the new one is adopted.