A Latin hymn from the 7th or 8th Century, it has gone through several translations. This one comes from the 1986 New English Hymnal.
Now that day light fills the sky,
We lift our hearts to God on high,
That He, in all we do or say,
Would keep us free from harm today;
Would guard our hearts and tongues from strife;
From anger’s din would shield our life;
From all ill sights would turn our eyes;
Would close our ears to vanities;
Would keep our inmost conscience pure;
Our souls from folly would secure;
Would bid us check the pride of sense
With due and holy abstinence.
So we, when this new day is gone,
And night in turn is drawing on,
With conscience by the world unstained
Shall praise His name for victory gained.
O God the Father, unto thee
Let everlasting glory be;
And glory to thine only Son,
With God the Spirit, ever one.