The Ten Plagues that were sent to persuade Pharaoh to let the Children of Israel leave Egypt. Originally the request was for temporary leave but the longer the negotiations dragged, the heavier the price became! That’s a lesson!
But what were the plagues and why did it require ten of them to change Pharaohs mind? Some argue that they were, except for the final one, all natural phenomena. Rivers do sometimes get clogged up with algae and change color. That kills the fish and they feed pests that then bring diseases which lead to dead carcasses that attract predators. And weather conditions affect migrating swarms and humidity affects climate and so on until we get to the only non-rational plague of killing the first born Egyptian sons. Natural catastrophes do not usually differentiate so specifically. But for the rest, perhaps the genius of Moses was that he knew how to make use of them.
Still, why start with plagues that Pharaoh’s magicians could imitate? The whole process teaches us something about doubt. We are cynical. We look for rational explanations and very often we can indeed find them. But we also often refuse to see the Divine even when it is there before our eyes. Pharaoh was like a modern logical fellow. He was suspicious of Moses and his talk of God. He wasn’t impressed by Moses’ tricks as he saw them, but still he was slowly becoming intrigued and as things progressed his own people started to pressurize him. Finally in stages he was brought to realize that there is more to life than science and logic.
In fact, we all need this kind of lesson today just as much as Pharaoh did three and half thousand years ago. We think we can manage without religion, until a crisis often makes us rethink our position.