What did Augustine mean by "The OT is the NT concealed. The NT is the OT revealed."? I've read this quote by Augustine several times over the years. Can you give me any examples of both parts of the quote to clarify it for me?
The Old Testament points forward to the coming of the promised Redeemer, the Serpent-crusher of Genesis, the Prophet like Moses, the Suffering Servant of Isaiah, the Son of David, the Messiah of Daniel, and the Humble King of Zechariah.

Four hundred years after God spoke to the prophet Malachi, God spoke again. The message was that the prophecy of Malachi 3:1 was soon to be fulfilled, that a prophet was to prepare the way for the Lord. The Messiah was on His way. That prophet was John the Baptist.

The New Testament Gospels reveal the promised Messiah, the Christ, in the person of Jesus of Nazareth. The Old Testament lays the foundation for the teachings and events found in the New Testament. The New Testament is only completely understood in the light of the events, characters, laws, sacrificial system, covenants, and promises of the Old Testament. In this way the promises contained in the Old Testament are revealed in the New Testament.