From The City of God, XVII.3 (426).

We read, “Behold, the days come, says the Lord, that I will make for the house of Israel, and for the house of Judah, a new testament: not according to the testament that I settled for their fathers in the day when I laid hold of their hand to lead them out of the land of Egypt; because they continued not in my testament, and I regarded them not, says the Lord. For this is the testament that I will make for the house of Israel: after those days, says the Lord, I will give my laws in their mind, and will write them upon their hearts, and I will see to them; and I will be to them a God, and they shall be to me a people,” (Heb. 8:8-10)… This pertains to both [the earthly and heavenly Jerusalem], for the city of God is called Jerusalem, and it is prophesied that the house of God shall be in it. And this prophecy seems to be fulfilled when King Solomon builds that most noble temple. For these things both happened in the earthly Jerusalem, as history shows, and were types of the heavenly Jerusalem. And this kind of prophecy, as it were compacted and commingled of both the others in the ancient canonical books, containing historical narratives, is of very great significance, and has exercised and continues to exercise greatly the wits of those who search holy scripture. For example, what we read of historically as predicted and fulfilled in the seed of Abraham according to the flesh, we must also inquire the allegorical meaning of, as it is to be fulfilled in the seed of Abraham according to faith.

St. Augustine (354-430) was a theologian and philosopher who served as Bishop of Hippo Regius in North Africa. He was a voluminous author, whose writings about God’s grace, the Sacraments, and the Church have been profoundly influential in the development of Western Christianity. The City of God was his greatest work, a wide-ranging discourse on the fall of the Roman Empire, the problem of evil, sin and redemption, and the interpretation of Scripture. His feast day is August 28.