It has the distinction of having been written by St. Gregory the Great (though some scholars dispute that and suggest its actual authorship is unknown.)
Nonetheless, it has a long and venerable history. Some background:
The Glory of These Forty Days is a 1906 translation by Anglican Minister, Maurice F. Bell (1862-1947) of the 6th century latin hymn Clarum Decus Jejunii, attributed to Pope St. Gregory the Great (540-604). It was traditionally sung at Matins during Lent. The Glory of These Forty Days is set to the Lutheran hymn tune Spires (Erhalt’ uns, Herr) by Joseph Klug (1523-1552). First published in 1543 with later harmonies added by J.S. Bach (1685-1750). In the Liturgy of the Hours it is used during Lent.
1. The glory of these forty days
we celebrate with songs of praise,
for Christ, through whom all things were made,
himself has fasted and has prayed.
2. Alone and fasting Moses saw
the loving God who gave the law,
and to Elijah, fasting, came
the steeds and chariots of flame.
3. So Daniel trained his mystic sight,
delivered from the lions’ might,
and John, the Bridegroom’s friend, became
the herald of Messiah’s name.
4. Then grant us, Lord, like them to be
full oft in fast and prayer with thee;
our spirits strengthen with thy grace,
and give us joy to see thy face.
5. O Father, Son and Spirit blest,
to thee be every prayer addressed,
who art in threefold name adored,
from age to age, the only Lord.
Enjoy the rendition below.