In contrast to the original creation, this new heaven and earth have neither sun nor moon, because they are lighted by the glory of God and their “lamp is the Lamb” (Rev. 21:23). John’s source for this imagery is Isaiah:
“No longer will you have the sun for light by day, nor for brightness will the moon give you light; but you will have the Lord for an everlasting light, and your God for your glory” (Isa. 60:19).
Jesus fulfills this prophecy when He comes into the world, as John tells us in both his gospel and his first epistle:
“In Him was life, and the life was the light of men. And the light shines in the darkness, and the darkness did not overpower it. …That was the true light which, coming into the world, gives light to every man” (John 1:4, 5, 9).
“God is light, and in Him is no darkness at all” (1 John 1:5).
“I am writing a new commandment to you, which is true in Him and in you, because the darkness is passing away, and the true light is already shining” (1 John 2:8).
The Light which shines from the new Jerusalem illumines the whole world, guiding into the city the kings of the land, as Isaiah prophesies:
“Arise, shine; for your light has come, and the glory of the Lord has risen upon you … The Lord will rise upon you, and His glory will appear upon you. And nations will come to your light, and kings to the brightness of your rising” (Isa. 60:1-3).
“The people who walk in darkness will see a great light; those who live in a dark land, the light will shine on them” (Isa. 9:2).
Matthew writes that Jesus’ ministry to the Gentiles fulfills the prophecies of Isaiah:
“[Jesus] withdrew into … the region of Zebulun and Naphtali. This was to fulfill what was spoken through Isaiah the prophet, saying, “The land of Zebulun and the land of Naphtali, by the way of the sea, beyond the Jordan, Galilee of the Gentiles: The people who were sitting in darkness saw a great light, and to those who were sitting in the land and shadow of death, upon them a light dawned” (Matt. 4:14-16).
Simeon, standing in the temple and holding the newborn baby Jesus in his arms, prophesied:
“For my eyes have seen Thy salvation, which Thou hast prepared in the presence of all peoples, a light of revelation to the Gentiles, and the glory of Thy people Israel” (Luke 2:30-32)
This light shines forth from the New Jerusalem without impediment because its gates are never closed in the daytime and there is no night there.
[For a more in-depth study see eschatology “Study Series 16 Lesson 9 Rev. Chapter 21”]