Exodus 11:9
And the Lord said to Moses, Pharaoh will not give ear to you, so that my wonders may be increased in the land of Egypt.
Exodus 7:3-4
And I will make Pharaoh's heart hard, and my signs and wonders will be increased in the land of Egypt.
Exodus 3:19
And I am certain that the king of Egypt will not let you go without being forced.
Exodus 10:1
And the Lord said to Moses, Go in to Pharaoh: for I have made his heart and the hearts of his servants hard, so that I may let my signs be seen among them:
Romans 9:16-18
So then, it is not by the desire or by the attempt of man, but by the mercy of God.