In Roman Catholic liturgy, Rex Gloriose Martyrum is the hymn at Lauds

Lauds

Lauds is a divine office that takes place in the early morning hours and is one of the two major hours in the Roman Catholic Liturgy of the Hours. In the Eastern Orthodox tradition, it forms part of the Office of Matins...

 in the Common

Common (liturgy)

The Common or common of saints is a part of the Christian liturgy that consists of texts common to an entire category of saints, such as Apostles or Martyrs...

 of Martyrs (Commune plurimorum Martyrum) given in the Roman Breviary. It comprises three strophe

Strophe

A strophe forms the first part of the ode in Ancient Greek tragedy, followed by the antistrophe and epode. In its original Greek setting, "strophe, antistrophe and epode were a kind of stanza framed only for the music," as John Milton wrote in the preface to Samson Agonistes, with the strophe...

s of four verses in Classical iambic dimeter, the verses rhyming in couplets, together with a fourth concluding strophe (or doxology

Doxology

A doxology is a short hymn of praises to God in various Christian worship services, often added to the end of canticles, psalms, and hymns...

) in unrhymed verses varying for the season.

The first stanza illustrates the metric and rhymic scheme:

Rex gloriose martyrum,

Corona confitentium,

Qui respuentes terrea

Perducis ad coelestia.

History

The hymn is of uncertain date and unknown authorship, Mone (Lateinische Hymnen des Mittelalters, III, 143, no. 732) ascribing it to the sixth century and Daniel (Thesaurus Hymnologicus, IV, 139) to the ninth or tenth century. The Roman Breviary text is a revision, in the interest of Classical prosody, of an older form (given by Daniel, I, 248). The corrections are: terrea instead of terrena in the line "Qui respuentes terrena"; parcisque for parcendo in the line "Parcendo confessoribus"; inter Martyres for in Martyribus in the line "Tu vincis in Martyribus"; "Largitor indulgentiæ" for the line "Donando indulgentiam". A non-prosodic correction is intende for appone in the line "Appone nostris vocibus". Daniel (IV, 139) gives the Roman Breviary text, but mistakenly includes the uncorrected line "Parcendo confessoribus". He places after the hymn an elaboration of it in thirty-two lines, found written on leaves added to a Nuremberg book and intended to accommodate the hymn to Protestant doctrine. This elaborated form uses only lines 1, 2, 4, 5, 6, 8, 9 of the original. Two of the added strophes may be quoted here to illustrate the possible reason (but also a misconception of doctrine in the apparent assumption of the lines) for the modification of the original hymn:

Velut infirma vascula

Ictus inter lapideos

Videntur sancti martyres,

Sed fide durant fortiter.

Non fidunt suis meritis,

Sed sola tua gratia

Agnoscunt se persistere

In tantis cruciatibus.