John literally writes that the Lord God will “light upon them,” that is, will shine his light in their direction so that they are able to see (Revelation 21:23–24) both himself and their surroundings. The point is that God’s servants bask in his presence such that the God-who-is-light enlightens their surroundings so that they have all the light they need to fulfill the tasks God as given them. More, this God-who-is-light gives such quality light that his servants do quality work, that is, they worship and see and reign in a manner pleasing to him.
5 And night will be no more. They will need no light of lamp or sun, for the Lord God will be their light, and they will reign forever and ever.