On Te Deum

I had never seen this hymn until a couple of years ago when it showed up in the liturgy at my church. This is an ancient hymn, dating back to the 4th or 5th century. I realize that it is not traditionally associated with Advent, but it is a beautiful expression of worship to our triune God.

Te Deum

You are God: we praise you; 
You are the Lord: we acclaim you;
You are the eternal Father:
All creation worships you.
To you all angels, all the powers of heaven,
Cherubim and Seraphim, sing in endless praise:
Holy, holy, holy, Lord, God of
      power and might,
heaven and earth are full of your glory.
The glorious company of apostles praise you.
The noble fellowship of prophets praise you.
The white-robed army of martyrs praise you.
Throughout the world the holy Church
      acclaims you:
Father, of majesty unbounded,
your true and only Son, worthy of all worship,
and the Holy Spirit, advocate and guide.
You, Christ, are the king of glory,
the eternal Son of the Father.
When you became man to set us free
you did not spurn the Virgin's womb.
You overcame the sting of death,
and opened the kingdom of heaven to all believers.
You are seated at God's right hand in glory.
We believe that you will come, and be our judge.
Come then, Lord, and help your people,
bought with the price of your own blood,
and bring us with your saints to glory everlasting.
Save your people, Lord, and bless your inheritance.
Govern and uphold them now and always.
Day by day we bless you.
We praise your name for ever.
Keep us today, Lord, from all sin.
Have mercy on us, Lord, have mercy.
Lord, show us your love and mercy;
for we put our trust in you.
In you, Lord, is our hope:
and we shall never hope in vain.

From Encyclopedia Orbis Latini:

Te Deum is a Latin hymn to God the Father and Christ the Son, traditionally sung on occasions of public rejoicing (coronation of kings, proclamation of bishops, consecration of a virgin, canonization of a saint, divulgation of a peace treaty or a victory).

According to legend, it was improvised antiphonally by St. Ambrose and St. Augustine at the latter's baptism. It has more plausibly been attributed to Nicetas, bishop of Remesiana in the early 5th century, and its present form--equal sections devoted to the Father and Son, a half-clause to the Holy Spirit, followed by a litany--fit in historically with part of the Arian controversy (over the nature of Christ) of the 4th century. Much of the text is composed of traditional statements of belief; and unlike most hymns, it is prose.

Hymn text sourced from Encyclopedia Orbis Latini.