Seven, as in Revelation 15:1, signifies everything in an universal sense. The number 'seven' was considered holy, as is well known, because of the six days of creation, and the seventh, which is the celestial self, where peace, rest, and the Sabbath is. The number seven occurs so frequently in the rites of the Jewish church and is held holy everywhere.

So times were divided into seven, longer and shorter intervals, and were called weeks, like the great intervals of times till the coming of the Messiah, in Daniel 9:24-25. The time of seven years is called 'a week' by Laban and Jacob, as in Genesis 29:27-28. So wherever the number seven occurs, it is considered holy and sacred, as in Psalm 119:164, and in Isaiah 30:26.

As the periods of a person's regeneration are distinguished into six, prior to the seventh, or the celestial self, so the times of vastation are also distinguished, until nothing celestial is left. This was represented by the many captivities of the Jews, and by the last Babylonian captivity, which lasted seven decades, or seventy years. This was also represented by Nebuchadnezzar, in Daniel 4:16, 22, 29. It also refers to the vastation of the end times, in Revelation 15:1, 7-8. They should 'tread the holy city under foot, forty and two months, or six times seven,' as in Revelation 11:2 and Revelation 5:1. So the severity and increments of punishment were expressed by the number seven, as in Leviticus 26:18, 21, 24, 28 and Psalm 79:12.

(参考: Apocalypse Explained 5, 7-8, 15; Arcana Coelestia 395; Daniel 9, 9:24, 9:25; Psalms 119)

Gates" in ancient times had a significance that does not hold in the modern world. Cities then were enclosed by walls for protection; gates in the walls let people in and out to do their business, but were also the weak points in the cities' defenses. In the Bible, cities on one level represent the minds of individual people. On a broader level, they represent beliefs shared by a community. The gates, then, represent openings where the Lord can feed us an understanding of truth and a desire for good. They also represent points where the hells can invade and sway us with false ideas and evil desires. We are kept in balance during our lifetimes, with influences from both the Lord and from hell. Ideally, we will over our lifetimes continue to invite the Lord farther and farther in and drive the hells back until ultimately the Lord can occupy our minds completely. And that point our belief in Him and His power and love will hold the gates and deny evil any entrance. As individuals, we at that point become angels. As communities, we at that point become part of the Lord's church. And at that point the gates become an entry point, introductory truths that allow people to enter churches and start bringing the Lord into their lives.