John the Apostle
Revelation 21:19ESV·traditional attribution

The foundations of the wall of the city were adorned with every kind of jewel. The first was jasper, the second sapphire, the third agate, the fourth emerald,

Matthew Henry Presbyterian @wholebiblehenry

We have already considered the introduction to the vision of the new Jerusalem in a more general idea of the heavenly state; we now come to the vision itself, where observe, I. The person that opened the vision to the apostle - one of the seven angels, that had the seven vials full of the seven last plagues, Rev 21:9.

Commenting on Revelation 21:9-27

John Gill Reformed Baptist @doctorgill

The fifth, sardonyx,.... Which is partly of the sardian, and partly of the onyx stone, which resembles a man's nail, from whence it has its name; it is reddish, bordering on white; it may be thought to answer to the onyx in the breastplate, on which was written the name of Joseph.

Albert Barnes Presbyterian @notesbybarnes

Verse 19. And the foundations of the wall of the city. . Were garnished. Were adorned, or decorated. That is, the foundations were composed of precious stones, giving them this highly ornamented and brilliant appearance. The first foundation. The first row, layer, or course. Barnes on "Re 21:14". Was jasper. . The second, sapphire. This stone is not elsewhere mentioned in the New Testament.