The canticle Dignus est agnus, (Worthy is the Lamb) is taken from Revelation 5:12-13b, 15:3b, 19:5b-6
Worthy is the Lamb who was slain
to receive power and riches and wisdom and strength
and honor and glory and blessing.
To him who sits on the throne and to the Lamb
be blessing and honor and glory and might forever and ever.
Great and marvelous are your works, Lord God Almighty.
Just and true are your ways, King of the Nations.
Who will not fear, O Lord, and glorify your name?
For you alone are holy.
Praise our God, all you his servants
and you who fear him, small and great.
Alleluia! For the Lord our God the Almighty reigns.
Alleluia! Alleluia! Amen.
Source: Common Service Book of the Lutheran Church, revised using phrases from The Holy Bible, Evangelical Heritage Version.
The canticle Dignus est agnus seems to have its origins in American Lutheranism in the late 19th century. It appeared in several service books beginning with the General Synod’s Church Book of 1868.
It appears on p. 122 of The Lutheran Hymnal (1941) without music. Earlier books prescribed its use as an option for the main canticle in Matins and Vespers (in place of the Te Deum or Magnificat). Later books suggested it as an alternative song of praise in the Common Service (in place of the Gloria in Excelsis).
In 2000 Years of Classic Christian Prayers, ed. Owen Collins, a similar text is given composed of several Bible verses from Revelation, attributed to Francis of Assisi (d. 1226):
Holy, holy, holy, Lord God Almighty, who was and who is and who is coming. (Revelation 4:8)
Worthy are you, our Lord and God, to receive the glory and the honor and the power, for you have created all things, and because of your will they existed and were created. (Revelation 4:11)
Worthy is the Lamb who was slain to receive power and riches and wisdom and strength and honor and glory and blessing. (Revelation 5:12)
Bless the Father, the Son and the Holy Spirit; sing praise to him and highly exalt him forever. (Song of the Three Holy Children)
Praise our God, all you his servants and you who fear him, small and great (Revelation 19:5)
Let every creature that is in heaven and on earth and under the earth and on the sea, and all that is in them say: To him who sits on the throne and to the Lamb be blessing and honor and glory and might forever and ever. (Revelation 5:13)
Glory be to the Father, and to the Son, and to the Holy Spirit.
Praise him and exalt him above all forever.
As it was in the beginning is now and will be forever.
Amen. Praise him and exalt him above all forever.
An article on Dignus est agnus by John Warwick Montgomery can be read here: http://www.ctsfw.net/media/pdfs/montgomeryhistoricalstudy.pdf
The text of this canticle has been reworked into a new canticle, This Is the Feast of Victory / Worthy Is Christ, by poet John W. Arthur. It first appeared as an anthem for choir, Festival Canticle: Worthy Is Christ with music by Richard W. Hillert, and made its first appearance in a hymnal in Lutheran Book of Worship as an alternative to the Gloria in Excelsis in the Divine Service.
This is the feast of victory for our God.
Alleluia, Alleluia, Alleluia.
1 Worthy is Christ, the Lamb who was slain,
whose blood set us free to be people of God. [Refrain]
2 Power, riches, wisdom and strength,
and honor, blessing and glory are his. [Refrain]
3 Sing with all the people of God
and join in the hymn of all creation.
4 Blessing, honor, glory and might
be to God and the Lamb forever. Amen. [Refrain]
For the Lamb who was slain
has begun his reign. Alleluia. [Refrain]
© 1978 Lutheran Church in America, The American Lutheran Church, The Evangelical Lutheran Church in Canada, and The Lutheran Church – Missouri Synod
Parts of this canticle are identical with the introit for Christ the King in the Roman rite. This is the Latin text:
Dignus est Agnus, qui occisus est, accipere virtutem, et divinitatem, et sapientiam, et fortitudinem, et honorem.
Ipsi gloria et imperium in saecula saeculorum.
Deus, judicium tuum Regi da: et justitiam tuam Filio Regis.