The appearance of Corpus Christi as a feast in the Christian calendar was primarily due to the petitions of the 13th century Augustinian nun Saint Juliana of Liège. From her youth she claimed that God had been instructing her to establish a feast day for the Eucharist and later in life petitioned the learned Dominican Hugh of St-Cher, Jacques Pantaléon (Archdeacon of Liège and later Pope Urban IV) and Robert de Thorete, Prince-Bishop of Liège. At that time bishops could order feasts in their dioceses, so in 1246 Bishop Robert convened a synod and ordered a celebration of Corpus Christi to be held each year thereafter. The decree is preserved in Anton Josef Binterim's Vorzüglichsten Denkwürdigkeiten der Christkatholischen Kirche, together with parts of the first liturgy written for the occasion.
The celebration of Corpus Christi only became widespread after both Juliana and Bishop Robert had died. In 1263, Jacques Pantaléon, now Pope Urban IV, investigated claims of a miracle in which blood had issued from a host. As a result, in 1264 he issued the papal bull Transiturus in which Corpus Christi was made a feast day. A new liturgy for the celebration was written by Saint Thomas Aquinas.
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