He has mercy on whom He wills, and whom He wills He hardens.

[Mr. M]

The narrative of Exodus shows that God is not random or capricious in whom He hardens.
Did not the Pharaohs claim to be deity and to rule by the will of Almighty God?
This same principle is true of the scribes and Pharisees, they were unable to repent, even
after witnessing miracles. Their hearts were hardened, as decreed in Isaiah 6.
Yeshua teaches on this here.
The Parable of the Two Sons Matthew 21:
28 But what do you think? A man had two sons, and he came to the first and said,
Son, go, work today in my vineyard.
29 He answered and said, I will not, but afterward he regretted it and went.
30 Then he came to the second and said likewise. And he answered and said, I will, sir,
but he did not go.
31 Which of the two did the will of his father?
They said to Him, The first.
Jesus said to them, “Assuredly, I say to you that tax collectors and harlots enter the
kingdom of God before you.
32 For John came to you in the way of righteousness, and you did not believe him;
but tax collectors and harlots believed him; and when you saw it, you did not afterward
repent and believe him.

Luke 7:
29 And when all the people heard Him, even the tax collectors justified God, having been baptized with the baptism of John.
30 But the Pharisees and lawyers rejected the will of God for themselves, not having been baptized by him.

 

[Mr. M]

Paul teaches on Moses and Pharaoh here.
Romans 9:
14 What shall we say then? Is there unrighteousness with God? Certainly not!
15 For He says to Moses, I will have mercy on whomever I will have mercy, and I will have
compassion on whomever I will have compassion.
16 So then it is not of him who wills, nor of him who runs, but of God who shows mercy.
17 For the Scripture says to the Pharaoh, “For this very purpose I have raised you up,
that I may show My power in you, and that My name may be declared in all the earth.
18 Therefore He has mercy on whom He wills, and whom He wills He hardens.
19 You will say to me then, “Why does He still find fault? For who has resisted His will?”
20 But indeed, O man, who are you to reply against God? Will the thing formed say to him
who formed it, “Why have you made me like this?”
21 Does not the potter have power over the clay, from the same lump to make one vessel
for honor and another for dishonor?
22 What if God, wanting to show His wrath and to make His power known, endured with much longsuffering the vessels of wrath prepared for destruction,
23 and that He might make known the riches of His glory on the vessels of mercy,
which He had prepared beforehand for glory,
24 even us whom He called, not of the Jews only, but also of the Gentiles?