Did God harden Pharaoh's heart?
Yes, but only after Pharaoh made the choice to harden his own heart to the point that he crossed the line of no return. He couldn't hear God speaking to him in a spiritual sense any more. The Bible clearly warns all of us not to harden our hearts. Our hearts are subject to become callused if we do not respond to God's conviction of sin in our lives. The Bible says that today is the day of salvation. It also says that no man comes to the Father unless the Spirit draws him. We don't choose the place and time to be saved on our own accord.
"But when Pharaoh saw that there was relief, he hardened his heart and would not listen to Moses and Aaron, just as the LORD had said" (Exodus 8:15).
"But this time also Pharaoh hardened his heart and would not let the people go" (Exodus 8:32).
"But the LORD hardened Pharaoh"s heart and he would not listen to Moses and Aaron, just as the LORD had said to Moses" (Exodus 9:12).