From Hilary of Poitiers, via Thomas of Aquinas, on the deep mystical meaning of this Sunday’s gospel:

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.