Te lucis ante terminum (Before the end of the light...)

A hymn/prayer against nightmares, mentioned in Canto VIII of Dante's Purgatorio.

"An old and venerable Ambrosian hymn from the 7th century for the close of day at Compline. This version is the one found in the Monastic Breviary and the Roman Breviary. The current version in the Liturgy of the Hours, which is given below, drops the second verse and replaces it with two other verses." [Source]

TE lucis ante terminum, rerum Creator, poscimus ut pro tua clementia sis praesul et custodia.	TO Thee, before the close of day Creator of the world, we pray that with Thy wonted favor, Thou wouldst be our Guard and Keeper now.
Procul recedant somnia et noctium phantasmata; hostemque nostrum comprime, ne polluantur corpora.	From all ill dreams defend our eyes, from nightly fears and fantasies: tread under foot our ghostly foe, that no pollution we may know.
Praesta, Pater piissime, Patrique compar Unice, cum Spiritu Paraclito regnans per omne saeculum. Amen.	O Father, that we ask be done through Jesus Christ Thine only Son, who, with the Holy Ghost and Thee, shall live and reign eternally. Amen.

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From the Roman Breviary, translation by J. M. Neale (1818-1866).