It is one of the hardest verses in Exodus. Why didn't the Lord simply strike Pharaoh dead and free the slaves?
The Targum Pseudo-Jonathan on Exodus 9:16, the Aramaic paraphrase preserved in the tradition of Yonatan ben Uzziel, gives the answer in the Lord's own voice: "Verily I have spared thee alive, not that I may benefit thee, but that My power may be made manifest to thee, and that My Holy Name may be made known in all the earth."
The Targumist makes two things painfully clear. First, Pharaoh's survival is not a kindness. He is not being rewarded. He is not being given another chance to become a tzaddik. Second, the reason he is kept alive is pedagogical — for display. So that My power may be made manifest. <p>The Maggid teaches: the Lord could have ended this story in a single night. Instead, He stretched it across ten plagues, because the world needed to see. Not only Egypt. All the earth. Every nation, every century, every Pesach Seder where a child asks why this night is different — the answer begins with Pharaoh's preservation.
The tyrant was spared so that the story could be told. That is a terrifying thought. But it is also the mechanism by which a slave people became a witness to the Name of God forever.