Hilary of Poitiers

In these things which were done concerning John, there is a deep store of mystic meaning. The very condition and circumstances of a prophet are themselves a prophecy. John signifies the Law; for the Law proclaimed Christ, preaching remission of sins, and giving promise of the kingdom of heaven. Also when the Law was on the point of expiring, (having been, through the sins of the people, which hindered them from understanding what it spake of Christ, as it were shut up in bonds and in prison,) it sends men to the contemplation of the Gospel, that unbelief might see the truth of its words established by deeds.