Rev 21:18

“"The city was from pure gold, similar to pure glass." He uses this strange analogy so that in all metaphors he might confer a unique dignity upon the one true stone, which is Christ, and so teach that all things serve him. For who does not know that gold is much different from glass and differs from it also in color? And although it is common that the church is symbolized by gold since it is often depicted by golden lampstands and bowls on account of its worship of Wisdom, nonetheless that pure gold is compared to pure glass is somewhat puzzling. I think the significance of this is given in what the apostle said, "Do not pronounce judgment before the time until the Lord comes, who will bring to light the things now hidden in darkness and will disclose the purposes of [our] hearts." For with glass nothing is seen on the outside that does not exist on the inside. And so, this book in announcing that time when the thoughts of each one will be openly declared to each other, boldly compares gold with glass. Whatever at that time will be in the thoughts of the saints shall shine with the adornment of the virtue of Wisdom.… But now, however much one might excel in virtue, "no one knows the thoughts of man except the spirit of the man which is in him."”

“The city itself was pure gold, like clear glass. The Church is figured as gold, often adorned with golden candlesticks and bowls for the sake of wisdom's cultivation. Glass, however, refers to true faith, because what is seen on the outside is also inside, and there is nothing simulated or opaque in the saints of the Church. It can also refer to that time when thoughts are clearly revealed to each other.”

“Jasper glimmers with a certain faint greenness and so shows the modest face of virginity. This is so that you might understand that our Lord Jesus Christ is joined to every building of the city and that that body taken from the flesh of the Virgin rises up for the protection of the whole wall. "The city itself was pure gold, pure as glass." In this most pure gold, which is purified by the heat of fire and so is proven, we perceive the chorus of the saints who have been tested in the furnace of suffering and by the heat of temptation and so have been made pure through the power of the Lord. They are compared with pure glass to indicate the transparent and pure brightness of the holiness that is in them.”

“And he says that the inner structure of its wall is jasper. Already we have received jasper as the symbol of the incorruptible and life-giving Christ. And he says the city is pure gold, like clear glass. The gold is arranged with brilliance and transparency. The precious and purity of the saints is presented in works and words.”