Albert Barnes Commentary Revelation 21:22

"And I saw no temple therein: for the Lord God the Almighty, and the Lamb, are the temple thereof." — Revelation 21:22 (ASV)

And I saw no temple therein. No structure built expressly for the worship of God; no particular place where he was adored. It was all temple—nothing but a temple. It was not like Jerusalem, where there was only one house built expressly for Divine worship, and to which the inhabitants resorted to praise God; it was all one great temple built in honor of his name, and where worship ascended from every part of it. With this explanation, this passage harmonizes with what is said in Revelation 2:12; Revelation 7:15.

For the Lord God Almighty and the Lamb are the temple of it. They are present in all parts of it in their glory; they fill it with light; and the splendor of their presence may be said to be the temple. The idea here is that it would be a holy world—all holy. No particular portion would be set apart for purposes of public worship, but in all places God would be adored, and every portion of it devoted to the purposes of religion.