“And afterward Moses and Aaron went in, and told Pharaoh, Thus saith the Lord God of Israel, Let my people go, that they may hold a feast unto me in the wilderness.” (Exodus 5:1)
The lesson that God taught Pharaoh, King of Egypt, was a steady, escalating lesson of humility, ending in the realization that the God of Israel is God. Moses made a simple request, “…Let my people go, that they may hold a feast unto [God] in the wilderness.” Pharaoh said no, and thus started his lessons.
The first 3 signs that God showed Pharaoh were the rod turning into a serpent, then the first two plagues: Water turning to blood and then a plague of frogs. All three of these first 3 signs were not only rejected by pharaoh, but were reproducible by Pharaoh’s magicians, the magicians rods became serpents, they made water turn to blood, “And the magicians of Egypt did so with their enchantments: and Pharaoh's heart was hardened, neither did he hearken unto them; as the Lord had said.” (Exodus 7:22) “And the magicians did so with their enchantments, and brought up frogs upon the land of Egypt.” (Exodus 8:7) The Lord knew that these wonders would prove ineffective, but also knew that the lesson was not finished.
The 4th through 10th plagues of Egypt were not reproducible by Pharaoh’s magicians (scientists). Also, unlike the first 2 plagues that affected everyone in Egypt, the 4th through 10th plagues never touched the land of Goshen or the Hebrew people. “And I will sever in that day the land of Goshen, in which my people dwell, that no swarms of flies shall be there; to the end thou mayest know that I am the Lord in the midst of the earth.” (Exodus 8:22) This was a tough pill to swallow for the magicians and Pharaoh, as illustrated by their thoughts during the 6th plague, “And the magicians could not stand before Moses because of the boils; for the boil was upon the magicians, and upon all the Egyptians.” (Exodus 9:11) During the 9th plague God plagued Egypt with darkness, “…darkness which may be felt.” Imagine a darkness that you could actually feel. Then the last plague and the Hebrews were still unaffected, because of the blood applied to their doorways. This 10th plague started the Passover tradition in remembrance of the Hebrews liberation from Egypt and God passing over them and sparing their firstborn children.
That’s not where Pharaoh’s lesson ended though. His people and advisors were still able to persuade him to go after the Hebrews, so his lesson still hadn’t been learned. It took a pillar of dark cloud holding them back, the Red Sea parting, the Hebrews walking across on dry land with walls of water on either side of them and the subsequent crashing down of the waters drowning all of Pharaoh’s chariots, horses and charioteers as they tried to follow God’s people. “And the children of Israel went into the midst of the sea upon the dry ground: and the waters were a wall unto them on their right hand, and on their left.” (Exodus 14:22) The Bible doesn’t say what Pharaoh felt or thought about the results of God’s Lesson, but the history of the Hebrews, after they cross the Red Sea, shows no documentation that the Egyptians pursued them. Pharaoh had learned his lesson and God’s people rejoiced.
“The Lord is my strength and song, and he is become my salvation: he is my God…” (Exodus 15:2)