Ex 8:15) But when Pharaoh saw that there was respite, he hardened his heart, and hearkened not unto them; as the LORD had said.
Ex 8:32) And Pharaoh hardened his heart at this time also, neither would he let the people go.
Ex 9:34) And when Pharaoh saw that the rain and the hail and the thunders were ceased, he sinned yet more, and hardened his heart, he and his servants.
God's will was for Pharaoh to let the Israelites go. God is not duplicitous. He would not have Moses tell Pharaoh to let Israel go, but then harden Pharaoh's heart so that he would not. That would make God untrustworthy.
In the OT, pretty much everything that happens is attributed to God, whether it's good or bad. In the NT, Jesus made known the spiritual war we are in, and that God is love, He is light, and in Him is no darkness at all.
You stopped the bold of the scripture in Exodus 8:15 right before it said this,
as the LORD had said.
These are the aforementioned verses re: God hardening Pharaoh's heart.
1599 Geneva Bible Exodus 7:2 Thou shalt speak all that I commanded thee: and Aaron thy brother shall speak unto Pharaoh, that he suffer the children of Israel to go out of his land.
3 But I will harden Pharaoh’s heart, and multiply my miracles, and my wonders in the land of Egypt.
4 And Pharaoh shall not hearken unto you, that I may lay mine hand upon Egypt, and bring out mine armies,
even my people, the children of Israel out of the land of Egypt, by great [
d]judgments. (13)
So Pharaoh’s heart was hardened, and he hearkened not to them, as the Lord had said.
Exodus 9:12 And the Lord hardened the heart of Pharaoh, and he hearkened not unto them, as the Lord had said unto Moses.
Exodus 10:1 Again the Lord said unto Moses, Go to Pharaoh, for I have hardened his heart, and the heart of his servants, that I might work these my miracles in the midst of his realm, [verse19 And the Lord turned a mighty strong West wind, and took away the grasshoppers, and violently cast them into the red Sea,
so that there remained not one grasshopper in all the land of Egypt.
20
But the Lord hardened Pharaoh’s heart, and he did not let the children of Israel go.
[verse 27 (But the Lord hardened Pharaoh’s heart, and he would not let them go.)
28 And Pharaoh said unto him, Get thee from me: look thou see my face no more: for whensoever thou comest in my sight, thou shalt die.
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Exodus 11:4And Moses said, Thus saith the Lord, About midnight will I go out into the midst of Egypt.
5 And all the firstborn in the land of Egypt shall die, from the firstborn of Pharaoh that sitteth on his throne, unto the firstborn of the maid servant, that is at the mill, and all the firstborn of beasts.
6 Then there shall be a great cry throughout all the land of Egypt, such as was never none like, nor shall be.
7 But against none of the children of Israel shall a dog move his tongue, neither against man nor beast, that ye may know that the Lord putteth a difference between the Egyptians and Israel.
8 And all these thy servants shall come down unto me, and fall before me, saying, Get thee out, and all the people that are at thy feet, and after this will I depart. So he went out from Pharaoh very angry.
9 And the Lord said unto Moses, Pharaoh shall not hear you, that my wonders may be multiplied in the land of Egypt.
10 So Moses and Aaron did all these wonders before Pharaoh: but the Lord hardened Pharaoh’s heart, and he suffered not the children of Israel to go out of his land.
Exodus 14:4 And I will harden Pharaoh’s heart that he shall follow after you:
so I will get me honor upon Pharaoh, and upon all his host: the Egyptians also shall know that I am the Lord: and they did so.
5 ¶ Then it was told the king of Egypt, that the people fled: and the heart of Pharaoh and of his servants was turned against the people, and they said, Why have we this done, and have let Israel go out of our service?
6 And he made ready his chariots, and took his people with him,
7 And took six hundred chosen chariots, and all the chariots of Egypt, and captains over every one of them.
8 (For the Lord had hardened the heart of Pharaoh king of Egypt, and he followed after the children of Israel: but the children of Israel went out with an high hand.)