« ANGELUS DOMINI ». — This phrase is used to designate the pious devotion whereby, at the sound of the bell in the morning, at midday, and at sunset, the faithful are invited to recite three Ave Maria, interspersed with three Gospel verses commemorating the Incarnation of Jesus and praising the Virgin Mother. From the first of those verses: A. D. etc., the pious practice took its name.
Just as the present-day formula of the Ave Maria was formed and spread throughout the Middle Ages, until it reached the form that has now become universal in the Church, so too must the same be said of the devotion of the A. D. Indeed, as early as the thirteenth century, the invitation to prayer with the Pater and the Ave at the sound of the bell at the time of completory and curfew was common. S. Bonaventura urged his friars to inculcate this pious practice among the faithful, and Giovanni XXII granted a special indulgence for it in Rome in 1327. From the beginning of the fourteenth century, the use of a similar prayer when the bell was rung in the morning is attested in many places; this custom entered into established practice during that and the following century. The ringing of the bell at midday for prayer was restricted in some dioceses to Fridays only; it was extended to every day when Callistus III, in 1456, invited prayers for victory against the Turks. From these customs, beginning in the sixteenth century, there developed the practice that still prevails today, and which popes Benedict XIV and Leo XIII endowed with special indulgences.