"The heavenly messenger measured the holy city and it was twelve thousand furlongs or fifteen hundred miles: the length and the breadth and the height of it were equal, as we have pointed out — a cube. Some have supposed that a literal city must be meant since various measurements are given. However, we must always keep in mind that this city is the bride, the Lamb’s wife! Therefore such dimensions must necessarily have a symbolical and spiritual meaning in relation to the body of Christ! The measurements are in multiples of twelve which are a symbol and signature of God’s purposes in His elect. The number twelve often enters into the symbolism of the book of Revelation — twelve tribes, twelve stars, twelve apostles, twelve angels, twelve foundations, twelve gates. So here the number twelve is found in the measurements of the city: each side is twelve thousand furlongs and the wall is one hundred and forty-four cubits, which is twelve times twelve."
Much more in the link:
https://www.godfire.net/eby/Rev/rev246.html
.
"Then I was made to know that the "twelve legions of angels" of which Jesus spoke is a symbol for the army of God. This knowledge stirred me tremendously! Think not, dear friend, that Jesus meant that He could call an exact number of heavenly messengers, for the number of soldiers in a legion was not fixed — it could run anywhere from about 3,000 to more than 6,000 men. Twelve is a symbolic number, a perfect number, a meaningful number, signifying GOVERNMENTAL PERFECTION. It is found as a multiple in all that has to do with RULE. Ed Vallowe, in his splendid book KEYS TO SCRIPTURE NUMERICS, has written, "This number, twelve, symbolizes God’s perfect, divine accomplishment actively manifested. It shows a completeness of a growth or administration. Twelve marks governmental perfection and is used as the signature of Israel. The number is used 187 times in the Bible. It is used 22 times in the book of Revelation. Twelve is the number for government by divine appointment. Jesus said to His disciples, Verily, I say unto you, that ye which have followed me, in the regeneration, when the Son of man shall sit in the throne of His glory, ye also shall sit upon twelve thrones, judging the twelve tribes of Israel’ (Mat. 19:28). The twelve apostles shall sit upon their twelve thrones and judge and rule in connection with our Lord’s rule upon His throne. They will occupy those twelve (symbolical) thrones by divine appointment."
Long quote in the link :)
https://www.godfire.net/eby/Rev/rev246.html
.