Ma'arif al-Qur'an
Mufti Muhammad ShafiIn verse 35, it was said: كَذَٰلِكَ يَطْبَعُ اللَّـهُ عَلَىٰ كُلِّ قَلْبِ مُتَكَبِّرٍ جَبَّارٍ (That is how Allah stamps a seal on the entire heart of an arrogant tyrant), that is, the way the hearts of Pharaoh and Haman remained unaffected by the good counsel of Sayyidna Musa (علیہ السلام) and the believer from the House of Pharaoh, similarly, Allah Ta’ ala cancels out or puts a seal on the heart of every such person who is arrogant and tyrannical (someone proud and arrogant, someone unjust and oppressive). When this happens, the effect is that the light of faith does not enter that heart, and one is rendered unable to distinguish between good and bad. In one قِرَأت (qira'ah: rendition of the Qur'an), the words for 'arrogant' and 'tyrant' have been identified as attributes of the heart for the reason that the heart is the reservoir of all morals and deeds. Every deed, good or bad, is born in the heart.
Therefore, it has been said in Hadith that there is a piece of flesh (heart) in the human body which, when it works right, it makes the whole body work right, and when it goes bad, it makes the whole body go bad. (Qurtubi)