One of the earliest Ambrosian hymns, 6th century or earlier, this hymn is used for Vespers from Easter Sunday until Ascension. In the Breviary revision of 1632 by Pope Urban VIII the hymn was so greatly altered that only three lines of the original remained and thus is really a different hymn entirely. The revised hymn can be found under the title of Ad regias Agni dapes. (source)
Ad cenam Agni providi,
Stolis salutis candidi,
Post transitum maris Rubri
Christo canamus principi.
Cujus corpus sanctissimum
In ara crucis torridum,
Sed et cruorem roseum
Gustando, Dei vivimus.
Protecti paschae vespero
A devastante angelo,
De Pharaonis aspero
Sumus erepti imperio.
Iam pascha nostrum Christus est,
Agnus occisis innocens;
Qui carnem suam obtulit.
O vera, digna hostia,
Per quam franguntur tartara,
Captiva plebs redimitur,
Redduntur vitae praemia!
Consurgit Christus tumulo,
Victor redit de barathro,
Tyrannum trudens vinculo
Et paradisum reserans.
Esto perenne mentibus
Paschale, Jesu, gaudium
Et nos renatos gratiae
Tuis triumphis aggrega.
Jesu, tibi sit gloria,
Qui morte victa praenites,
Cum Patre et almo Spiritu,
In sempiterna saecula. Amen.
The Lamb’s high banquet we await
In snow-white robes of royal state;
And now, the Red Sea’s channel past,
To Christ our Prince we sing at last.
Upon the altar of the cross
His body hath redeemed our loss;
And tasting of His roseate blood,
Our life is hid with Him in God.
That Paschal Eve God’s arm was bared,
The devastating angel spared;
By strength of hand our hosts went free
From Pharaoh’s ruthless tyranny.
Now Christ, our Paschal Lamb, is slain,
The Lamb of God that knows no stain,
The true Oblation offered here,
Our own unleavened Bread sincere.
O Thou, from whom hell’s monarch flies,
O great, O very Sacrifice,
Thy captive people are set free,
And endless life restored in Thee.
For Christ, arising from the dead,
From conquered hell victorious sped,
And thrust the tyrant down to chains,
And paradise for man regains.
We pray Thee, King with glory decked,
In this our Paschal joy, protect
From all that death would fain effect
Thy ransomed flock, Thine own elect.
To Thee who, dead, again dost live,
All glory, Lord, Thy people give;
All glory, as is ever meet,
To Father and to Paraclete. Amen.
English translation by John Mason Neale (1818-1866).