First of all, the Scripture about the Hebrew Exodus has been read and the words of the mystery have been explained as to how the sheep was sacrificed and the people were saved.
Therefore, understand this, O beloved: The mystery of the passover is new and old, eternal and temporal, corruptible and incorruptible, mortal and immortal in this fashion:
It is old insofar as it concerns the law, but new insofar as it concerns the gospel; temporal insofar as it concerns the type, eternal because of grace; corruptible because of the sacrifice of the sheep, incorruptible because of the life of the Lord; mortal because of his burial in the earth, immortal because of his resurrection from the dead.
The law is old, but the gospel is new; the type was for a time, but grace is forever. The sheep was corruptible, but the Lord is incorruptible, who was crushed as a lamb, but who was resurrected as God. For although he was led to sacrifice as a sheep, yet he was not a sheep; and although he was as a lamb without voice, yet indeed he was not a lamb. The one was the model; the other was found to be the finished product.
For God replaced the lamb, and a man the sheep; but in the man was Christ, who contains all things.
Hence, the sacrifice of the sheep, and the sending of the lamb to slaughter, and the writing of the law, each led to and issued in Christ, for whose sake everything happened in the ancient law, and even more so in the new gospel.
For indeed the law issued in the gospel–the old in the new, both coming forth together from Zion and Jerusalem; and the commandment issued in grace, and the type in the finished product, and the lamb in the Son, and the sheep in a man, and the man in God.
For the one who was born as Son, and led to slaughter as a lamb, and sacrificed as a sheep, and buried as a man, rose up from the dead as God, since he is by nature both God and man.
He is everything: in that he judges he is law, in that he teaches he is gospel, in that he saves he is grace, in that he begets he is Father, in that he is begotten he is Son, in that he suffers he is sheep, in that he is buried he is man, in that he comes to life again he is God.
Such is Jesus Christ, to whom be the glory forever. Amen.
Melito of Sardis (d. 180 A.D.), Peri Pascha (On the Passover)