Bede the Venerable — as excerpted in the Catena Aurea on Luke 1:23-25

“And yet Elisabeth conceives John, because the more inward parts of the Law abound with sacraments of Christ. She conceals her conception five months, because Moses in five books set forth the mysteries of Christ; or because the dispensation of Christ is represented by the words or deeds of the saints, in the five ages of the world.”