This hymn is used for Vespers on Sundays and Weekdays in Lent from the First Sunday in Lent through Passion Sunday in the Extraordinary Form of the Roman Breviary. It is used for Vespers on Sundays in Lent until Holy Week in the Ordinary Form. It was used for Vespers during Lent from Ash Wednesday to Passion Sunday in the Paris Breviary (1736). It was used for Lauds during the first three weeks on Lent in the Sarum Breviary.
This is the text as it appears in Hymns Ancient and Modern (1867):
O Merciful Creator, hear;
(1)To us in pity bow Thine Ear:
Accept the tearful prayer we raise
In this our fast of forty days.
Each heart is manifest to Thee;
Thou knowest our infirmity:
Repentant now we seek Thy Face;
Impart to us Thy pardoning Grace.
Our sins are manifold and sore,
But spare Thou them who sin deplore;
And for Thine own Name’s sake make whole
The fainting and the weary soul.
Grant us to mortify each sense
By means of outward abstinence,
That so from every stain of sin
The soul may keep her fast within.
Blest Three in One, and One in Three,
Almighty God, we pray to Thee,
That Thou wouldst now vouchsafe to bless
Our fast with fruits of righteousness. Amen.
Words: Pope St. Gregory the Great (I), 6th Century; tr. John Mason Neale, 19th Century, alt.
Tune: “Audi Benigne Conditor” Gregorian Chant, Tone II, traditional.
Alternate Tune: “Ford” Thomas Ford, 1614.
(1) Another version of the text renders this line as “In tender pity bow Thine ear:”
The original Latin text of this hymn may be found here.