Revelation 21:15-21
(Rev 21:15 KJV)
And he that talked with me had a golden reed to measure the city, and the gates thereof, and the wall thereof.

In Revelation 11:1-2, John was given a reed to measure the temple of God but here the angel had a golden reed and he is to use it to measure the city, the gates, and the wall. Again we see this as a symbolic measurement. In Revelation 11:2, John was told to leave out the court outside the temple but here the measurement is going to be done and nothing will be left out. This city would be too magnificent for any human builder to build and that is why we can know from this description that this city was made by God without any human hands plus it is an apocalyptic description of the body of believers.

(Rev 21:16 KJV)
And the city lieth foursquare, and the length is as large as the breadth: and he measured the city with the reed, twelve thousand furlongs. The length and the breadth and the height of it are equal.

In many commentaries we are told that the New Jerusalem is going to be a perfect cube which will be suspended between Heaven and Earth. This is erroneous because we are looking at apocalyptic language and to make it literal, where it is not supposed to be literal, will only yield a false interpretation. What we have in view here is a perfect cube and the measurements would be 1500 miles on each side. Now the size is not important here but what is being taught here is that the New Jerusalem is a perfect city without so much as one inch being incorrect. All the measurements are totally equal which means that all who are part of this city are equal in the eyes of God because every redeemed believer had to come through the cross and therefore no one holds a more exalted position. The perfection and equality of this cube is what is in view not living quarters.

(Rev 21:17 KJV)
And he measured the wall thereof, an hundred and forty and four cubits, according to the measure of a man, that is, of the angel.

In the previous verse we are told that the measurements are all equal being 12,000 furlongs which would translate into 1,500 miles. In this verse we are being told that the wall is 144 cubits which would equal 216 feet if we use the cubit as 18 inches. Would that be 144 cubits in height? Length? Breadth? It does not say because we are seeing a figure and not a literal wall with a literal measurement. Remember in Revelation 7 and 14, we were introduced to the 144,000 which represented the fullness of all the believers who were saved from the first to the last. Here we are seeing that the wall is 144 cubits which is 12 X 12. 12 is the number of fullness which is in view. The 144 is given to us here as a reminder that the wall is really the completed body of believers. In Ephesians 2:19-22, we read that the believers are being fit and built together which would be symbolized by the construction of some type of edifice, and in this case it would be the wall because it is being spoken of as 144 cubits which represents the fullness of what is in view.

(Rev 21:18 KJV)
And the building of the wall of it was of jasper: and the city was pure gold, like unto clear glass.

In Revelation 4:3 we saw that John had used Jasper to describe God. Jasper, as you recall, is an opaque stone but was described as a clear stone. In Revelation 21:11, the jasper stone is equated with the glory of God. Now here the building of the wall is of jasper and that would indicate that the glory of God is present in this city and that the jasper stone would be describing the believers as being pure as the clearness of the stone and reflecting the glory of God within themselves. Then the city is described as being pure gold like unto clear glass. Gold is a very heavy opaque precious metal but here it is being described as clear as glass. Gold is always identified with salvation.
(1 Cor 3:12 KJV) Now if any man build upon this foundation gold, silver, precious stones, wood, hay, stubble; Gold, silver, and precious stones are identified with the Gospel. The imagery in Rev. 21:18, is once again teaching us of the purity of the redeemed believers. The blood of Christ has so cleansed the believer that they are described as gold but as clear glass.

(Rev 21:19-20 KJV)
{19} And the foundations of the wall of the city were garnished with all manner of precious stones. The first foundation was jasper; the second, sapphire; the third, a chalcedony; the fourth, an emerald;{20} The fifth, sardonyx; the sixth, sardius; the seventh, chrysolyte; the eighth, beryl; the ninth, a topaz; the tenth, a chrysoprasus; the eleventh, a jacinth; the twelfth, an amethyst.

Now we are introduced to the foundations of the wall which are made of twelve different precious stones. Once again the number twelve plays a prominent part because we had seen that there were four sides to the city and four walls but here we are being told that there are twelve adornments of the foundations which means the fullness of whatever is in view. The jasper was a deep green stone. The sapphire is probably the ancient lapis lazuli which had a sprinkling of iron pyrite in it. Chalcedony was a generic name for stones such as agate, carnelian, or sardius. The emerald was bright green and we saw that the emerald rainbow surrounded the throne. Sardonyx was a variety of agates. Sardius was a blood-red precious stone. Chrysolyte was like yellow topaz. Beryl was sea-green precious stone. Topaz was a golden topaz sometimes with a greenish tint. Chrysoprasus was a variety of quartz but with a green tint. Jacinth was probably a type of zircon with a bluish tint. Amethyst is a purple or blue-violet type of glassy quartz. What God is stating here with all these precious stones is that they are a foundation on which the Gospel is built.
(1 Cor 3:12 KJV) Now if any man build upon this foundation gold, silver, precious stones, wood, hay, stubble; (1 Cor 3:11 KJV) For other foundation can no man lay than that is laid, which is Jesus Christ. The Gospel is built upon the Lord Jesus Christ who is the foundation of Salvation for all the redeemed of God.

(Rev 21:21 KJV)
And the twelve gates were twelve pearls: every several gate was of one pearl: and the street of the city was pure gold, as it were transparent glass.

(Mat 13:45-46 KJV) Again, the kingdom of heaven is like unto a merchant man, seeking goodly pearls: {46} Who, when he had found one pearl of great price, went and sold all that he had, and bought it. Once again we are given an association with the Gospel. The one who sought the pearl of great price was the Lord Jesus Christ who gave His all to redeem the one pearl which is the entire body of believers. The twelve gates were twelve pearls. Each individual gate was of one pearl. Now that is a clue that we are not looking at anything literal. Pearls do not grow to the size of 216 feet. What we have here is that the believers are the pearls which the Lord Jesus Christ gave all for and because we see the number twelve again, it is the fulness of all the believers in glory. Then we are shown that the street of the city was pure gold as transparent glass. This would be representative of the entire city because here we are being told that only one street looks like this. The purity of that gold is a representative of true salvation. So we are seeing that salvation permeates the entire city of the New Jerusalem which means that no unsaved person can ever come in.