31 Then follows: “A garden shut up is my sister, my bride: a garden shut up, a fountain sealed.” That which is shut up and sealed reminds us of the mother of our Lord who was a mother and a Virgin. Hence it was that no one before or after our Saviour was laid in his new tomb, hewn in the solid rock. And yet she that was ever a Virgin is the mother of many virgins. For next we read: “Your shoots are an orchard of pomegranates with precious fruits.” By pomegranates and fruits is signified the blending of all virtues in virginity. “My beloved is white and ruddy”; white in virginity, ruddy in martyrdom.
And because He is white and ruddy, therefore it is immediately added “His mouth is most sweet, yea, he is altogether lovely.” The virgin bridegroom having been praised by the virgin bride, in turn praises the virgin bride, and says to her: “How beautiful are your feet in sandals, O daughter of Aminadab,” which is, being interpreted, a people that offers itself willingly. For virginity is voluntary, and therefore the steps of the Church in the beauty of chastity are praised. This is not the time for me like a commentator to explain all the mysteries of virginity from the Song of Songs; I have no doubt that the fastidious reader will turn up his nose at what has already been said.
Source: Against Jovinianus (New Advent)