Ex 4:21 And the LORD said to Moses, "When you go back to Egypt, see that you do all those wonders before Pharaoh which I have put in your hand. But I will harden his heart, so that he will not let the people go.
When God hardens a heart, He always does so, not arbitrarily, but as a punishment. God is a God of love. He wants all men to repent. He does not want any to perish.
However, if man stubbornly refuses to repent, God, as punishment, will give him over to his depraved and rebellious heart. Someone said that there are two kinds of people in the world: a) There are people who say to God: "Your will be done" and b) There are people to whom God says: "Your will be done."
Ps 81:12 So I gave them over to their own stubborn heart, To walk in their own counsels.
Ro 1:23 and changed the glory of the incorruptible God into an image made like corruptible man--and birds and four-footed animals and creeping things.
24 Therefore God also gave them up to uncleanness, in the lusts of their hearts, to dishonor their bodies among themselves,
25 who exchanged the truth of God for the lie, and worshiped and served the creature rather than the Creator, who is blessed forever. Amen.
26 For this reason God gave them up to vile passions. For even their women exchanged the natural use for what is against nature.
When God hardens a man's heart, He just simply stops calling him or her to repent and withholds the converting grace which was repeatedly rejected and refused.
