In the second section of the Book of Exodus, G-d begins the process that will lead to the redemption of the Jews from Egyptian slavery. After some preparations, G-d then begins to strike the Egyptians with plagues.
Exodus 6:2–9:35
The first nine plagues can be divided into three sets of three, each of which was intended to teach Pharaoh and the Egyptians something about the belief in G-d:
• The first set of three plagues (blood, frogs, and lice) was intended to demonstrate G-d’s existence.
• The second set (the mixed horde, epidemic, and inflammation
of the skin) was intended to demonstrate G-d’s providence.
• The third set (hail, locusts, and darkness) was intended to demonstrate G-d’s supernatural power.
Thus, the plagues teach us that not only does G-d exist; He also directs the world and wishes to come to our aid, and that He can and does override the natural order.
--Daily Wisdom Volume 3