«PRIMO DIE QUO TRINITAS». – Hymn of Matins of the ordinary Sunday Office; by an unknown author; it is found in manuscripts of the ninth century (C. Dreves – C. Blume, Anal. hymn., LI. Lipsia 1908, pp. 24–26).
It celebrates the greatness of the day consecrated to the Lord. Since the hymn was intended for the Office of the night, it invites the faithful to interrupt their sleep in order to raise their praise to the Lord, so that he may be more favorable to our supplications, purify us from impurities, and make us worthy of the heavenly homeland.
BIBL.: S. G. Pimont, Les hymnes du Bréviaire, Parigi 1874, I, pp. 21–38; C. Albin, La poésie du Bréviaire, Lione s. 2., pp. 1–6; F. Vanderstuif, Les hymnes de l'Ordinaire du Bréviaire romain, Parigi 1912; p. 56; A. Mirra, Gli inni del Breviario romano, Napoli 1947, p. 52. Silverio Mattei