John the Apostle
Revelation 21:2ESV·traditional attribution

And I saw the holy city, new Jerusalem, coming down out of heaven from God, prepared as a bride adorned for her husband.

Matthew Henry Presbyterian @wholebiblehenry

We have here a more general account of the happiness of the church of God in the future state, by which it seems most safe to understand the heavenly state. I. A new world now opens to our view (Rev 21:1): I saw a new heaven and a new earth; that is, a new universe; for we suppose the world to be made up of heaven and earth.

Commenting on Revelation 21:1-8

John Gill Reformed Baptist @doctorgill

And I John saw the holy city,.... The same with the beloved city in Rev 20:9 the church of God: sometimes the church militant is called a city, of which the saints are now fellow citizens, governed by wholesome laws, and enjoying many privileges; but here the general assembly and church of the firstborn, or all the elect of God, are intended, the whole body...

Albert Barnes Presbyterian @notesbybarnes

Verse 2. And I John saw the holy city, new Jerusalem, coming down from God out of heaven. On the phrase "new Jerusalem," ; . Here it refers to the residence of the redeemed, the heavenly world, of which Jerusalem was the type and symbol.