Charles Ellicott Commentary Exodus 11:9-10

"And Jehovah said unto Moses, Pharaoh will not hearken unto you; that my wonders may be multiplied in the land of Egypt. And Moses and Aaron did all these wonders before Pharaoh: and Jehovah hardened Pharaoh`s heart, and he did not let the children of Israel go out of his land." — Exodus 11:9-10 (ASV)

And the Lord said ... —The series of the nine wonders performed by Moses and Aaron is concluded with this short summary, of which the main points are:

1. God had said (Exodus 4:21) that the miracles would fail to move Pharaoh;
2. He had assigned as the reason for this failure His own will that the wonders should be multiplied (Exodus 7:3);
3. The miracles had now been performed;
4. Pharaoh had not been moved by them;
5. God had hardened his heart, as a judgment upon him, after he had first himself hardened it.

The result had been a series of manifestations calculated to impress the Israelites with a sense of God’s protecting care, and the Egyptians and neighbouring nations with a sense of His power to punish.