"The first [water, Ex. 7:17 ff.]: “My soul refuses to be comforted” (v. 2). Here the water of pleasure has been turned into blood, so that one cannot drink it or have pleasure in drinking it, for such water is blood and death for the soul.
The second [frogs, Ex. 8:2 ff.]: “And was exercised” (v. 3). Here are born the frogs that weary the soul with their harsh croaking. They are the memories and remnants of past sins that make the soul sick of pleasures.
The third [gnats, Ex. 8:16 ff.]: “And my spirit swooned away” (v. 3). This third sign is effective. The magicians of Egypt cannot imitate it, because here is the finger of God (Ex. 8:18). A man, too, can turn water into blood and pleasure into disgust, as well as stir up the croaking of frogs and the clamor of the conscience, but they cannot produce gnats. These are the tiny flies that sting and bite sharply without noise. They denote the proddings of conscience and remorse.
The fourth [flies, Ex. 8:21 ff.]: “My eyes awaited the night watches” (v. 4). Here follows the putting out of the evil light, so that now one does not want to see the things that are of the world. This is what flies of a different kind do. They keep us from seeing external things. And so “God has given them the spirit of insensibility, eyes that they should not see” (Rom. 11:8).
The fifth [death of the cattle, Ex. 9:3 ff.]: “I have been troubled,” or, according to the Hebrew, “I was stunned.” Here he becomes confounded and senseless, when the promptings of the flesh and its lusts are killed like cattle, the tickling of desire and of all that is in the world ceases.
The sixth [boils, Ex. 9:9 ff.]: “And I did not speak” (v. 4). He sends boils and ulcers in the sixth place. These inflict suffering so that they impose silence on all sins, so that there is no desire either to speak or to think of them. Often, indeed, we are not even moved, and still we think and speak about evils.
The seventh [hail, Ex. 9:18 ff.]: “I thought upon the days of old” (v. 5). These are the hard and strong thoughts about the coming Judgment. They crush everything green, everything that sprouts from the flesh.
The eighth [locusts, Ex. 10:4 ff.]: “And I meditated in the night with my own heart” (v. 6). This is the locust, incessantly gnawing at the carnal soul and eating into its vigorous flesh.
The ninth [darkness, Ex. 10:21 ff.]: “And I was exercised” (v. 6). This is a darkness that is felt for three days. During that time nothing can be seen or done, so that, instead of the lust of the flesh and of the eyes and the pride of life, faith, hope, and charity, which those three would darken, might shine forth.
The tenth [death of the firstborn, Ex. 12:29 ff.]: “And I searched my spirit” (v. 6). Here the firstborn are killed."