Today is the feast of St. Peter Damian, so I thought I'd talk a little a bit about his letter 78 to John of Lodi, in which he discusses the plagues of Egypt, interpreting them spiritually as a description of wordly life, and connecting them to the Ten Commandments. As he says, "the plagues that occurred in Egypt are nothing but wounds. And what was this heavenly Law if not medicine for these wounds?" (pp. 172-173). He interprets the plagues thusly:
First Plague: Water into Blood, "when the mind, blind to its own condition, disturbs and violates the purity of the true faith" (p. 173) -- faith, like water, gives nourishment. The first commandment is the remedy for this vice, insisting on the purity of divine worship. (Damian actually quotes Deuteronomy 6:4 as the first commandment, and takes it to cover both Dt. 5:7 and 5:8.)
Second Plague: Swarm of Frogs. Frogs are noisy, like "heretics and philosophers" (p. 173), and they live in the mud, just as the heretics and philosophers who chatter nonsense about the faith make their home among the unbelieving masses. The remedy for this vice is the commandment against taking the name of the Lord in vain.
Third Plague: Swarm of Gnats, "the vice of wandering and restlessness" (p. 174), since by their stinging they make it impossible to stay in one place. This restlessness leads to treating sin lightly, and thus as remedy God in the Decalogue commands that we keep the sabbath holy as a day of rest. (As an interesting side note, St. Peter reads the first three commandments as Trinitarian: the first is appropriated to the Father, the second to the Son, and the third to the Holy Spirit, and notes in favor of this that it was the third plague that the magicians of Egypt ascribed to the "finger of God" in Exodus 8:19, which is of course, a name for the Holy Spirit. And, of course, there is the old tradition that the first three commandments, pertaining to God directly, were written on the first tablet and the rest on the second.)
Fourth Plague: Swarm of Flies, which Damian, influenced by St. Isidore, interprets as dog-fleas, which leads to probably the most strained of the interpretations. Dogs are not respectful to their parents, and their fleas make them especially bad-tempered, so the remedy for this is honoring your parents.
Fifth Plague: Death of Cattle. To commit adultery is to be like the beasts, as when Jeremiah 5:7-8 associates adulterers with horses, so the remedy for this is the command against adultery. (This sounds a bit strained, but actually I think this is a quite salvageable association, because cattle and prosperous fertility are associated in the ancient world.)
Sixth Plague: Wounds and Boils. Wounds suggest hatred; boils suggest pride; their festering suggests anger. So the sixth commandment, against killing, is applied as a medicine to it.
Seventh Plague: Hail Mingled with Fire. Ice and fire are opposites, but here they are combined. "Thus those who steal the property of others are both frozen in regard to fraternal charity and on fire with the ardor of their cupidity" (p.177). The thundering and lightning of the storm suggests fear, and the plague is quite clearly one that would be damaging to property. Thus the remedy is the commandment against stealing.
Eighth Plague: Locusts. Locusts are little creatures that destroy all life, so they are fitting symbol for slanderers and false accusers, destroying all the good in their path, ruining harvests of good deeds, and gnawing at the lives of others with specious lies. Thus the eighth commandment, which remedies it, is the commandment against false witness.
Ninth Plague: Darkness on the Land. The coveter of another's wife is someone who acts from an interior darkness, a secret unfaithfulness in his heart. Thus God commanded Israel not merely that they should not run away with or defile their neighbor's wives, which the commandment against adultery covered, but that they should not even covet.
Tenth Plague: Death of the Firstborn. St. Peter takes the death of the firstborn to represent the self-poisoning character of our attachments to worldly things and pleasures, by which we lose our spiritual inheritance rights. Thus the remedy for it is the tenth commandment, not to covet our neighbor's goods.
"On Mount Sinai, that is, on the heights of a holy way of life, we must heal all these plagues that we endured in Egypt, all the internal forms of disease that we had contracted on the even ground of the secular life" (p. 180).
One can wonder whether anything can be made of all this, but even if the Damianian interpretation is wrong in some aspects, (1) no Christian can deny that Egypt represents the worldly life; (2) it is entirely plausible that the plagues in some ways represent the sins of Egypt -- for instance, even commentators with no intention of doing any allegorical reading have often noted that the striking of the waters as the very first volley is a blow against the Egyptian religion, in which the Nile was closely linked with the gods, which, as can easily be seen, fits the scheme; so (3) the only question really is whether we should divide up the plagues individually, as Damian does, or whether we should simply take them collectively.
Peter Damian, Letters 61-90, Blum, tr. CUA Press (Washington, DC: 1992).