In the Bible, exactly why did God force that guy to re-change his mind?

Appearing before Pharaoh, Moses and Aaron delivered their message in the name of Jehovah. But Pharaoh arrogantly said: “Who is Jehovah, so that I should obey his voice to send Israel away? I do not know Jehovah at all and, what is more, I am not going to send Israel away.” (Exodus 5:1, 2) Pharaoh proved to be both hardhearted and deceitful, yet Jehovah urged Moses to deliver messages to him again and again. (Exodus 7:14-16, 20-23; 8:1, 2, 20) Moses could see that Pharaoh was irritated.