Pharaoh did not know who the children of Israel were; he did not know who their God was; Pharaoh did not even know who he was, that he was a mere man, whom the God of heaven had put on the throne of Egypt. He needed to hear a message from God,
“Then the LORD said to Moses, ‘Rise early in the morning and stand before Pharaoh, and say to him, “Thus says the LORD God of the Hebrews: ‘Let My people go, that they may serve Me, for at this time I will send all My plagues to your very heart, and on your servants and on your people, that you may know that there is none like Me in all the earth’”’” (Exodus 9:13-14).
What a hard way to learn about God and that we must do what He says. Does He have to do harsh things with you that you might listen to Him?