Romans 9:18

So then he hath mercy on whom he will, and whom he will be hardeneth.

God chose the message of salvation (it's conditions and contents). Mercy will be extended to those that exercise obedient faith in Christ (Mark 16:16); all that can't handle that, or don't like it, will be 'hardened'.

And how does God harden? It is the result of God deliberately forcing. person to choose..(God gave Pharaoh. command that Pharaoh didn't like (but Pharaoh could of obeyed it, he was able but unwilling), God kept pressing the issue, and Pharaoh kept refusing. The Bible points out that Pharaoh 'hardened his own heart' (Romans 8:15; Romans 9:34), it reminds us that Pharaoh was. willing contributor to his stubbornness. "It is well within God's right to demand obedience of ANY MAN. It is God's right to demand obedience of any man even if he knows that that man will not obey. It is never unjust of God to demand obedience of one of his subjects.'

But someone might say, 'But why did God pick on "this" particular Pharaoh?' (1) Being 'picked on' can result in my salvation. God 'picked on' the people of Nineveh, they repented! (Jonah 3:1). God 'picked on Saul', and he became. Christian! (Acts 9:1) (2) In the final analysis, God picks on everyone in one degree or another (God picked on you when someone confronted you with the truth and challenged your former view of life). The question isn't, 'It's not fair that God picked on me', but rather, 'How am. going to respond to the commandments of my Creator?' (Matthew 28:19)

In fact, we might also add, that. number of times, what seemed to make Pharaoh more stubborn, was when God showed Pharaoh some mercy. (Exodus 2:28; Exodus 2:27; Exodus 2:24; Exodus 2:15 'but when Pharaoh saw that there was relief, he hardened his heart..'). Some people grow more stubborn when it seems that God is slow in exercising his wrath.