Exode 7:3

But I will harden the disposition of Pharoh's heart to multiply My signs and My wonders in the land of Mizraim.

One can ask , if Hashem hardened his heart what was his sin? The answer is that Hashem gave wisdom to man, and placed insight into his heart to be able to draw additional power to increasegood, or to detract from his evil, as i will explain later .......But the reason for the hardening of his heart is to increase My miracles. Rabbi Yeshua states the reason was to allow him to suffer the plagues, and he speaks incorrectly.

AND I WILL HARDEN PHARAOH’S HEART. The Rabbis said in Midrash Rabbah: “G-d revealed to Moses that He was destined to harden Pharaoh’s heart in order to bring judgment upon him for he caused them to work in cruel bondage.” It is also stated there [in Midrash Rabbah]:, 13:4. “For I have hardened his heart. Rabbi Yochanan said, ‘This provides a pretext for the heretics to say that G-d did not allow Pharaoh to repent.’ Rabbi Shimon ben Lakish said, ‘The mouths of the heretics be closed! Only, if it concerneth the scorners, He scorneth them. When He warns one on three occasions and he does not turn from his ways, He closes the door of repentance on him in order to punish him for his sin. Such was the case with wicked Pharaoh. After the Holy One, blessed be He, sent him five times [the request to let His people go] and he paid no attention to His words, the Holy One, blessed be He, said to him: You have stiffened your neck and hardened your heart; I will double your defilement.’”
The Rabbis [in the above Midrash] have thus discussed the question which all ask: “If G-d hardened his heart, what then was Pharaoh’s sin?” For this there are two explanations, and both of them are true. One is that Pharaoh in his wickedness had unjustifiably perpetrated such great evils against Israel that justice required that the ways of repentance be withheld from him, as is so indicated in many places in the Torah and in the Writings., where he quotes from the Prophets and Writings to substantiate this point. He was judged according to his wickedness which he had originally committed of his own will. The second explanation is that half of the plagues came upon him because of his transgressions, for in connection with them it is only said: And Pharaoh’s heart was hardened; And Pharaoh hardened his heart., 8:28 and 9:7. Thus Pharaoh refused to let the children of Israel go for the glory of G-d. But when the plagues began bearing down upon him and he became weary to suffer them, his heart softened and he bethought himself to send them out on account of the onslaught of the plagues, not in order to do the will of his Creator. Then G-d hardened his spirit and made his heart obstinate, so that His name may be declared [throughout all the earth]. Similar in meaning is the verse, Thus will I magnify Myself, and sanctify Myself, and I will make Myself known in the eyes of many nations, and they shall know that I am the Eternal. And that which He said before the plagues, And I will harden his heart, and he will not let the people go, was merely His warning to Moses of that which He was destined to do to Pharaoh in the last [five] plagues, it being similar to that which He said, And I know that the king of Egypt will not give you leave to go., 3:19. This then is the meaning of the verse [before us], And I will harden Pharaoh’s heart, and multiply My signs. That is to say, “I will harden his heart so that My wonders may be multiplied in the land of Egypt,” since in the last five plagues, as well as at the drowning in the sea, it is said, And the Eternal hardened the heart of Pharaoh,, 14:8. for the king’s heart is in the hand of the Eternal; He turneth it whithersoever He will.

ואני אקשה, seeing that G’d is interested in the sinner’s repentance rather than his death (as we know from Ezekiel 33,11 חי אני, נאום ה', אם אחפוץ במות הרשע כי אם בשובו מדרכו וחיה, “by My life, I do not want the death of the wicked but that he return from his wicked path and live”), G’d told Moses that He would bring on numerous plagues, all in order to increase the chances that Pharaoh would finally see the light and become a genuine penitent. He hoped that by demonstrating His greatness and His power this would eventually cause the Egyptians to recognise all this. At the same time, G’d also spelled out a similar thought in 9,16 but aimed at the Israelites, when He said: “that the only reason He had not yet killed Pharaoh was so that in the course of more plagues you, the Jewish people, would come to recognise both G’d’s greatness and His patience.“ He also wanted the Jewish people to learn how to both love and revere Him when they witnessed and thought about the meaning of all these plagues. There can be no question that without G’d stiffening Pharaoh’s attitude from time to time, he would have collapsed much sooner and would have sent the Israelites on their desired journey. However, this would not have been the result of his repentance and humbling himself before the Lord, involving genuine regret about his previous errors, but the result of his impotence to withstand the pressure applied to him. He would have acted out of terror of what the next plague would do to him and to his country. If we needed confirmation of this, all we have to do is look at what his servants said to him when Moses threatened with the plague of locust. They said to him: “how long will you be obstinate, do you not see that Egypt will go down the drain?!” There was not a single word of regret of past errors, no word of recognition that G’d could have killed them all long before this and that He must therefore be very patient, and kind, but mere terror forced them to utter these words. (10,7) Keeping all this in mind, it is foolish to ask how G’d could punish Pharaoh after he Himself had interfered with his decision-making process by “stiffening his heart,” ואני אקשה את לב פרעה, I will stiffen the heart of Pharaoh, etc.” not in order to punish him but in order to finally trigger repentance in his heart. The operative clause is “in order that I can demonstrate all these miracles of Mine in his midst” (10,1), the purpose being to bring about his humbling himself in repentance and genuine contrition. If that wish of G’d would indeed materialise, the Jewish people also would tell of G’d’s greatness, (למען ספר את שמי, having observed at first hand how the mightiest secular power on earth turned into G’d fearing human beings.) They would tell their children and children’s children the lesson they had learned that G’d’s apparent cruelty is actually an act of loving kindness as it results in His creatures coming to love and to revere Him. [Noach, who had survived the destruction of mankind by a deliberate act of G’d’s kindness to him and his family, had not been able to relate to his children what G’d hoped that the Israelites would be able to relate to their children. Ed.] The basic lesson in ethics we derive from all this is that when suffering an affliction we must first and foremost examine our past actions to find out where we went wrong, and try to find out what these afflictions are intended to trigger in our memory so that we can improve our conduct both vis-à-vis G’d and our fellow man.