Rom 9:17-18
17 For the scripture saith unto Pharaoh, Even for this same purpose have I raised thee up, that I might shew my power in thee, and that my name might be declared throughout all the earth.
18 Therefore hath he mercy on whom he will have mercy, and whom he will he hardeneth.
That's Preaching so that God's Name might be declared throughout all the Earth, the Truth that "whom he will he hardeneth"
That's Part of the Gospel of God's Grace, that God in His Sovereignty has the right to and does harden men unto destruction, He denies them Mercy unto Salvation,so that they may continue in their native disobedience fitting themselves even more for destruction as vessels of wrath they were made ! Rom 9:19-22
19 Thou wilt say then unto me, Why doth he yet find fault? For who hath resisted his will?
20 Nay but, O man, who art thou that repliest against God? Shall the thing formed say to him that formed it, Why hast thou made me thus?
21 Hath not the potter power over the clay, of the same lump to make one vessel unto honour, and another unto dishonour?
22 What if God, willing to shew his wrath, and to make his power known, endured with much longsuffering the vessels of wrath fitted to destruction:
God had a right to make and form some men for the purpose of wrath and destruction, Just like He did with Pharaoh, as an Illustration !
God raised him up, gave him existence and being to demonstrate how He makes men for a destructive purpose.
Rom 9:17-18
17 For the scripture saith unto Pharaoh, Even for this same purpose have I raised thee up, that I might shew my power in thee, and that my name might be declared throughout all the earth.
18 Therefore hath he mercy on whom he will have mercy, and whom he will he hardeneth.
It was God that harden pharaohs heart, Paul is referring to the scripture here Ex 4:21
21 And the Lord said unto Moses, When thou goest to return into Egypt, see that thou do all those wonders before Pharaoh, which I have put in thine hand: but I will harden his heart, that he shall not let the people go.
Paul"s point here is that God harden Pharaohs heart, and not that pharaoh hardened his own heart since He did not mention that part, but only the part about God hardening his heart !
You see Pharaoh could not resist hardening his own heart because he was under God's Power to do so, that's why These Two things are said #1 Pharaoh had to harden his own heart becauseRom 9:17
17 For the scripture saith unto Pharaoh, Even for this same purpose have I raised thee up, that I might shew my power in thee, and that my name might be declared throughout all the earth.
Because God's Power was at work in him causing him to harden his own heart !
#2 To show that he could not resist hardening his own heart because God will was causing itRom 9:19
19 Thou wilt say then unto me, Why doth he yet find fault? For who hath resisted his will?
You see that ? That's the logical conclusion of this doctrine of the Gospel, If God is the one really in control causing pharaohs disobedient behavior, then why does God find fault with him ? After all he is only doing what God has caused him to do ! How is that Fair ? Now is not that how most of us think about this situation recorded here if indeed God is causing pharaoh to be disobedient and hardened ?