664. And after three days and a half.- That this signifies when completed, thus the end of the old church, and the beginning of a new church, is evident from the signification of three days and a half, as denoting fulness or completion at the end of the old church, when there is the beginning of a new church, concerning which see above (n. 658). The reason why it is said, after three days and a half, is, that days, in the Word, signify states, here, the last state of the church. For all times, in the Word, as hours, days, weeks, months, years, and ages, signify states in the Word, as in this case, the last state of the church, when there is no longer any good of love or truth of faith remaining. Because days signify states, and since in the first chapter of Genesis the establishment of the Most Ancient Church is treated of which was accomplished successively from one state to another, therefore it is said there that there was evening and there was morning the first, the second, the third, the fourth, the fifth, and sixth days, unto the seventh, when it was completed (Genesis 1:5, 8, 13, 19, 23, 31), and the days there do not mean days, but the successive states of the regeneration of men at that time, and the consequent establishment of the church with them. So also elsewhere in the Word.

Going up refers to going towards spiritual and celestial things, for these are inward things, and are also believed to be higher. Going down refers to going towards natural and earthly things, for these are outward things, and also appear lower.

(References: Arcana Coelestia 5406)