And because [the children of Jacob] were greatly afflicted and oppressed in a cruel slavery, and they groaned and cried to God, the God of the patriarchs, of Abraham, of Isaac and of Jacob, He led them out of Egypt by the hand of Moses and Aaron, striking the Egyptians with ten plagues, sending, in the last plague, a slaughtering angel, slaying their first-born, from man even unto beast.

He saved the sons of Israel from this, revealing in a mystery the Passion of Christ, by the slaughtering of a spotless lamb and by its blood given to be smeared on the houses of the Hebrews as a guard of invulnerability: the name of this mystery is the Pasch, source of liberation.

–Irenaeus, On the Apostolic Preaching