« RERUM DEUS TENAX VIGOR ». — Hymn of the hour of none, corresponding to three in the afternoon, attributed, though not with complete certainty, to St. Ambrose (cf. G. M. Dreves — C. Blume, Anal. hymnica, L, Leipzig 1907, p. 19). According to the manuscript tradition, it would belong to the Irish-Anglo-Saxon group (ibid., LI, Leipzig 1908, p. xx ff.).
At this hour the Church once again raises her voice of praise and prayer to the Lord and asks him that, as the light of day disappears, the light may draw near in which the soul may immerse itself, without seeing the setting of the sun, in eternal glory.
BIBL.: G. S. Piment, Les hymnes du Bréciaire romain, I, Paris 1874, p. 76; F. Vanderstyl, Les hymnes du Bréciaire romain, Paris 1912, p. 42.