Charles Spurgeon Commentary Revelation 21:23

"And the city hath no need of the sun, neither of the moon, to shine upon it: for the glory of God did lighten it, and the lamp thereof [is] the Lamb." — Revelation 21:23 (ASV)

And the city had no need of the sun, neither of the moon, to shine in it; for the glory of God did lighten it, and the Lamb is the light thereof.

Outward means are abolished when their mission is accomplished.

And the city had no need of the sun, neither of the moon, to shine in it: for the glory of God did lighten it, and the Lamb is the light thereof.

We have need of both the sun and the moon while we are in this world; if it were not for the great central luminary, the solar system would cease to be, and this earth and the moon and all their sister planets would die out in darkness. But when the sun has been turned into darkness, and the moon into blood, it will still be said of this holy city, the new Jerusalem, that the glory of God lightens it, and the Lamb is the light thereof.

See how blessedly God and the Lamb are linked together, for Father and Son are truly one. It is pleasant also to reflect that he who is the light of the world is also the light of the world that is yet to be revealed: the Lamb is the light thereof.