6 But observe what Himself says, “The things which were written in the law, and in the prophets, and in the Psalms concerning me.” And we know that the law extends from the time of which we have record, that is, from the beginning of the world: “In the beginning God made the heaven and the earth.” Thence down to the time in which we are now living are six ages, this being the sixth, as you have often heard and know. The first age is reckoned from Adam to Noah; the second, from Noah to Abraham; and, as Matthew the evangelist duly follows and distinguishes, the third, from Abraham to David; the fourth, from David to the carrying away into Babylon; the fifth, from the carrying away into Babylon to John the Baptist; the sixth, from John the Baptist to the end of the world.
Moreover, God made man after His own image on the sixth day, because in this sixth age is manifested the renewing of our mind through the gospel, after the image of Him who created us; and the water is turned into wine, that we may taste of Christ, now manifested in the law and the prophets. Hence “there were there six water-pots,” which He bade be filled with water. Now the six water-pots signify the six ages, which were not without prophecy. And those six periods, divided and separated as it were by joints, would be as empty vessels unless they were filled by Christ.
Why did I say, the periods which would run fruitlessly on, unless the Lord Jesus were preached in them? Prophecies are fulfilled, the water-pots are full; but that the water may be turned into wine, Christ must be understood in that whole prophecy.
Source: Tractates on the Gospel of John (New Advent)