Rav Hirsch: Vaeira II
On closer inspection we find the three groups of plagues are in intimate relation to the three phases which formed the pith of the Egyptian exile. Being strangers, servitude and suffering, was the progressive nature of the fate which Egypt’s crime against Israel inflicted. Being strangers, servitude and suffering were the conditions, which the plagues brought on the Egyptians ti impress them with the falsity of their assumed superiority, and to bring home to them the actual bitterness of the misery they dealt to their unhappy victims.
The first of each of the three groups of plagues, Blood, Wild Beasts, and Hail, showed the Egyptians how they themselves were no better than strangers in their own land, and how little justification they could find for treating the Jews as strangers and depriving them of all civil rights.
The second plague in each group, Frogs, Plague, and Locusts, showed them the emptiness of the pride and masterfulness, which the possession of slaves produces.
The third plague in each group, Lice, Boils, and Darkness, finally were sufferings which made them feel for themselves what it meant to have to submit to a systematic suffering.
The Slaying of the First Born finally brought the whole to a climax and accomplished their redemption.