In his own description of the early years of the Order, the Libellus de Principiis Ordinis Praedicatorum, composed sometime between December 25, 1231, and July 3, 1234, Jordan explains that the practice of singing the Salve Regina after Compline was begun after the freeing of a friar from a diabolical possession:

This cruel harassment of Brother Bernard was the first occasion that moved us to establish the custom of singing the Salve Regina after Compline at Bologna. From there the practice spread through the province of Lombardy and eventually became general throughout the Order. How many tears of devotion have sprung from this holy praise of Christ’s venerable Mother? How many hearts of those who sang or listened has it not melted, how often has it not softened bitterness and installed fervor in its place? Do we believe that the Mother of our Redeemer is pleased with such praises and moved by such cries? A certain man, both religious and trustworthy, has told me that, in spirit, he often saw the Mother of our Lord prostrate before her Son praying for the security of the whole Order, as the friars were singing: "Turn, then, most gracious advocate, thine eyes of mercy towards us." I mention this so that the brethren reading it may be inspired to even greater devotion in praising the virgin.¹⁵ 

While the Cistercians had already adopted the custom of singing the Salve in processions after their chapters, the Dominicans placed its singing at the close of Compline, with a procession from the choir to Our Lady’s altar.¹⁶  The community knelt at the words "Turn then, most gracious advocate, thy eyes of mercy on us" and were sprinkled with holy water by the hebdomadarian.¹⁷  This sprinkling is perhaps derived from Premonstratensian and Cistercian rituals.

Jordan’s Libellus recounts Mary’s role in bringing Reginald, a master of theology and dean of the cathedral chapter at Orleans, to the Order. During a serious illness in 1218, Our Lady healed him and, then, according to Jordan’s account: "showed him the whole habit of the Order."¹⁸  The Legenda Petri Ferrandi, composed by the Spanish Dominican, Peter Ferrandus, between 1235 and 1239, records the event, with the words of Mary: "Then she showed him the habit of the Order of Preachers. ‘Behold,’ she said, ‘this is the habit of your Order.’"¹⁹ 

Taken literally, Jordan and Ferrandus may mean only that Mary indicated the order which Reginald should enter by showing its habit. However, these texts have come to be understood as meaning that Mary gave Reginald a new habit or an additional element to the habit. Jacobus de Voragine, in his Legenda Aurea, written about 1260, asserts that Dominic received the same vision as had Reginald: "He heard all about the master’s [Reginald’s] vision and adopted the habit the Virgin had shown: the friars had been wearing surplices."²⁰ 

¹⁵ Jordan, The Libellus of Blessed Jordan, 120, in Biographical Documents, 82. Libellus de Principiis Ordinis Praedicatorum, CXX, Monumenta Historica Sancti Patris Nostri Dominici, MOPH, XVI (Roma: Institutum Historicum Fratrum Praedicatorum, 1935), 81.

¹⁶ Henri Leclercq, "Salve Regina," in Dictionnaire d’archéologie chrétienne et de liturgie, XV (Paris: Librairie Letouzey et Ané, 1948), 719.

¹⁷ Humbertus de Romanis, Super Constitutiones Fratrum Praedicatorum, II, xlii, De Vita Regulari, II, 129-130.

¹⁸ "Nichilominus etiam ei omnem huius ordinis habitum demonstravit." Jordan, Libellus, LVII, MOPH, XVI, 52.

¹⁹ "Tunc ei habitum ordinis Predicatorum ostendit: ‘En,’ inquit, ‘hic est habitus ordinis tui.’" Petrus Ferrandus, Legenda Petri Ferrandi, 35, MOPH, XVI, 235.

²⁰ Iacopo da Varazze, Legenda Aurea, II, ed. Giovanni Paolo Mazzioni, 728; Jacobus de Voragine, The Golden Legend, II, 50.