There was given me a reed like unto a rod; and the angel stood, and said unto me, Rise, and measure the temple of God, and the altar, and them that worship therein (Rev. 11:1)

And concerning the New Jerusalem:

The wall of the New Jerusalem was great and high, having twelve gates, and over the gates twelve angels, and names written, which are the names of the twelve tribes of the sons of Israel; on the east three gates, on the north three gates, on the south three gates, on the west three gates. The wall of the city had twelve foundations, and in them the names of the twelve apostles of the Lamb. He that talked with me had a golden reed, to measure the city, and the gates thereof, and the wall thereof. The city lieth four square, and the length thereof is as great as the breadth. And he measured the city with the reed, twelve thousand furlongs; the length and the breadth and the height thereof are equal. He measured the wall thereof, a hundred and forty and four cubits, which is the measure of a man, that is, of an angel (Rev. 21:12-17).

[2] The number "twelve" occurs here throughout, which is a very holy number because it signifies the holy things of faith (as said above, at verse 3 of this chapter, and as will be shown, of the Lord's Divine mercy, at the twenty-ninth and thirtieth, chapters of Genesis). And therefore it is added that this measure is the "measure of a man, that is, of an angel." It is the same with the new Temple and new Jerusalem in Ezekiel which are also described as to their measures (40:3, 5, 7, 9, 11, 13-14, 22, 25, 30, 36, 42, 47; 41:1 to the end; 42:5-15; Zech. 2:1-2). Here too regarded in themselves the numbers signify nothing but the holy celestial and spiritual abstractedly from the numbers. So with all the numbers of the dimensions of the ark (Exod. 25:10); of the mercy seat; of the golden table; of the tabernacle; and of the altar (Exod. 25:10, 17, 23; 26, and 27:1); and all the numbers and dimensions of the temple (1 Kings 6:2-3), and many others.