Since the other numbers in Revelation have been symbolic, WHY should we take the thousand years at 20:2 as a literal, set-in-stone number? I think that it too is symbolic. The number is ten cubed. We are told at 20:1 that the dragon, Satan, and the devil are all one. This is definitely an unholy trinity, only it is only three names for one unholy created being. Note well the words of 20:10! Forever is a VERY long time. Also verses fourteen and fifteen.
“And He who sits on the throne said, ‘Behold, I am making all things new.’ And He said, ‘Write, for these words are faithful and true.’ And He said to me, ‘It is done. I am the Alpha and the Omega, the beginning and the end. I will give to the one who thirsts from the spring of the water of life without cost. He who overcomes shall inherit all these things, and I will be his God and he will be My son. But for the cowardly and unbelieving and abominable and murderers and immoral persons and sorcerers and idolaters and all liars, their part will be in the lake that burns with fire and brimstone, which is the second death’” (21:5-8). Consider these words very carefully. Strive always in life to be amongst those who overcome and do not be at all a part of the latter group.
Remember that the act of measuring demonstrates ownership. The “size” of the city here measured is not as important as the fact that it is a cube–perfect. The measurements in the Greek are not the fifteen hundred miles reported in most of our Bibles, but twelve thousand stadia. The distance is the same, but the meaning of the numbers is different. The wall was not measured as “72 yards” either, but as 144 cubits. This equals 72 yards, but again the significance is different.
The fact that the city gates are never closed tell us of its security–there is no need to fear for only the godly are allowed into it; God the Father and God the Son illumine it!
“Do not seal up the words of this prophecy for the time is near!” (21:10). That is to say, do not hide these words from anyone, they need to know them because what is prophesied herein is about to happen NOW (the first century AD). Read 21:6, 7, 10, 12, 20 carefully and thoughtfully. All should heed the warning of 20:18-19 as well, they concern not only this book of Revelation, but the entire book of the Word of God, the Bible.