|94| Where, as in religious communities, the offices of the Church are performed in their full order, there follows on Matins that custom peculiar to Christmas, the celebration of Midnight Mass. On Christmas morning every priest is permitted to say three Masses, which should in strictness be celebrated at midnight, at dawn, and in full daylight. Each has its own Collect, Epistle, and Gospel, each its own Introit, Gradual, and other anthems. In many countries the Midnight Mass is the distinctive Christmas service, a great and unique event in the year, something which by its strangeness gives to the feast of the Nativity a place by itself. Few Catholic rites are more impressive than this Midnight Mass, especially in country places; through the darkness and cold of the winter's night, often for long distances, the faithful journey to worship the Infant Saviour in the splendour of the lighted church. It is a re-enactment of the visit of the shepherds to the cave at Bethlehem, aglow with supernatural light. Various symbolical explanations of the three Masses were given by mediaeval writers. The midnight celebration was supposed to represent mankind's condition before the Law of Moses, when thick darkness covered the earth; the second, at dawn, the time of the Law and the Prophets with its growing light; the third, in full daylight, the Christian era of light and grace. Another interpretation, adopted by St. Thomas Aquinas, is more mystical; the three Masses stand for the threefold birth of Christ, the first typifying the dark mystery of the eternal generation of the Son, the second the birth of Christ the morning-star within the hearts of men, the third the bodily birth of the Son of Mary.{8} At the Christmas Masses the "Gloria in excelsis" resounds again. This song of the angels was at first chanted only at Christmas; it was introduced into Rome during the fifth century at Midnight Mass in imitation of the custom of the Church of Jerusalem.{9}