This hymn is used for None on Sundays and Weekdays throughout the year in the Extraordinary form and the Ordinary Form.
Rerum, Deus, tenax vigor,
Immotus in te permanens,
Lucis diurnae tempora
Largire clarum vespere,
Quo vita numquam decidat,
Sed praemium mortis sacrae
Perennis instet gloria.
Praesta, Pater piissime,
Patrique compar Unice,
Cum Spiritu Paraclito
Regnans per omne saeculum. Amen.
Words: Attr. St. Ambrose, 4th C.
Tune: “Rerum Deus Tenax Vigor” Gregorian Chant, Mode II, traditional.*
*This tone is used for Sundays throughout the year. There are a number of other musical settings for this hymn.
This hymn has been translated as “O Thou True Life of All that Live.”