This hymn was used for Compline during Christmastide and on the Nativity of the BVM (Sept. 8) and All Saints (Nov. 1) in the Sarum Breviary.
This is the text as it appears in Hymns Ancient and Modern (1867):
O Saviour of the world forlorn,
This day to save us Thou wast born;
Protect us through the coming night,
And ever save us by Thy Might.
Now, Lord, be Thou in mercy nigh,
And spare Thy servants when they cry;
Our sins blot out, our prayers receive,
Thy Light throughout our darkness give.
O let not sleep the soul oppress,
Nor secret foe the heart possess;
Our flesh keep chaste, that it maybe
A holy temple unto Thee.
To Thee, Who makest souls anew,
Our hearts in prayer would humbly sue,
That pure and free from inward stain
We from our beds may rise again.
All praise to God the Father be,
All praise, Eternal Son, to Thee,
Whom with the Spirit we adore
For ever and for evermore. Amen.
Words: Anonymous, 6th-7th C.; tr. Rev. William John Copeland (1804-1885)
Tune: “Song 5” Orlando Gibbons, 1583-1625 .
The original Latin text of this hymn may be found here.