From “Sermon 46.5-8” (ca. 1160).
This birthday is more of a celebration than the feasts of other saints precisely because it is so clearly symbolic and prophetic. Since by his preaching and baptizing, yes, and by his way of living, and by the manner of his death and the miracle of his birth the Voice foretold the World, the Forerunner ran before the Lord, the Prophet prefigured the Coming One, the More-than-a-Prophet actually pointed out the actual Lord, the Messenger was able to pick out the very One he heralded, and not just the benefit of those in this world, but for those in the other one.
So it was that one born contrary to the laws of nature prefigured to some extent the One who would be born beyond such laws; the former against the normal, the latter beyond the natural; the unusual in the first case, the unique in the other. While there had never been an instance of the latter, there had been a few of the former. Elizabeth’s sterility partly prefigured Mary’s virginity. There is pregnant sterility on the one hand, fruitful virginity on the other. The old wife brought forth an only son for the sake of the one and only Son the young virgin gave birth to.
John’s father was decrepit with age. Christ’s Father knows nothing of age. For just as the lack of any Scriptural genealogy for Melchizedek typifies the indescribable birth of Christ. Zachary’s old age suggests Christ’s not having a human father. An old man begets in the former, no man begets in the latter instance. The one unable to beget by nature did so by grace; neither nature nor grace did any begetting when the Giver of grace and nature’s Maker alone effected everything.
Thus it was only right that the foreshadowing should ever decrease and the actual fact should ever increase. Shadows, as you know, are no longer at morning and evening, and shorter than midday than the bodies that cast them. This holds when morning stands for prophecy, evening for memory, and midday for the actuality of Christ. Consequently, it was for John to grow less while Christ grew greater, for Christ to be lifted up in death while John became less by decapitation, for Christ to be born as day increased, and John as day decreased.
Isaac of Stella (ca. 1100-ca. 1170) was an English Cistercian monk, theologian and philosopher, who was abbott of monasteries at Stella in Western France and on the nearby Ile de Re. He wrote a widely influential commentary on the Mass and several philosophical works that aimed to reconcile Aristotelian and Neo Platonic philosophy. His sermons were preached to his fellow monks. The translation is adapted from The Selected Works of Isaac of Stella: A Cistercian Voice from the Twelfth Century, tr. D Deme, (Aldershot: Ashgate, 2007).