Rabbi Shlomo Ephraim Luntschitz (1550-1619), known by his magnum opus, Kli Yakar, explains that the mnemonic teaches us that ten plagues are divided into three categories, and each set of plagues came to teach Pharaoh one principle.
The first set - Blood, Frogs and Lice - were there to teach Pharaoh about the existence of Hashem. The first set of plagues thus begins with the verse “With this you shall know that I am Hashem” (Exodus 7:17).
The second set - Wild Beasts, Pestilence and Boils - were to teach Pharaoh that Hashem is intricately involved in the world and the lives of each individual. This set of plagues differentiates between the oppressed Israelites and the Egyptian oppressors (Exodus 8:18), to show that Hashem in fact does involve Himself in the lives of people on Earth. He acts not only on a country as a whole, but distinguishes communities and individuals.
The third set Hail, Locusts, Darkness, Death of the Firstborn, was there to teach Hashem’s omnipotence. Pharaoh believed there was more than one power, therefore this set of plagues states “In order that you may know that there is none like Me in all the world” (Exodus 9:14).
To believe in God is to believe in the possibility that things can be different to how they are today.
To believe that God cares about everyone and everything is to believe that everyone and everything is here for a purpose. Each of us can make a positive difference in the world.
To believe that there is none but God means that there is no moment in our lives that cannot be deeply meaningful and infinitely significant.