The word(s) "hearts" appears 132 time(s) in 121 verse(s) in Quran in Mohsin Khan translation.

(21) O Messenger (Muhammad صلى الله عليه وسلم)! Let not those who hurry to fall into disbelief grieve you, of such who say: "We believe" with their mouths but their hearts have no faith. And of the Jews are men who listen much and eagerly to lies - listen to others who have not come to you. They change the words from their places; they say, "If you are given this, take it, but if you are not given this, then beware!" And whomsoever Allah wants to put in Al-Fitnah [error, because of his rejecting of Faith], you can do nothing for him against Allah. Those are the ones whose hearts Allah does not want to purify (from disbelief and hypocrisy); for them there is a disgrace in this world, and in the Hereafter a great torment.

(22) And you see those in whose hearts there is a disease (of hypocrisy), they hurry to their friendship, saying: "We fear lest some misfortune of a disaster may befall us." Perhaps Allah may bring a victory or a decision according to His Will. Then they will become regretful for what they have been keeping as a secret in themselves.

(23) They said: "We wish to eat thereof and to satisfy our hearts (to be stronger in Faith), and to know that you have indeed told us the truth and that we ourselves be its witnesses."

(24) And of them there are some who listen to you; but We have set veils on their hearts, so they understand it not, and deafness in their ears; and even if they see every one of the Ayat (proofs, evidence, verses, lessons, signs, revelations, etc.) they will not believe therein; to the point that when they come to you to argue with you, the disbelievers say: "These are nothing but tales of the men of old."

(25) When Our Torment reached them, why then did they not humble themselves (believe with humility)? But their hearts became hardened, and Shaitan (Satan) made fair-seeming to them that which they used to do.

(26) Say (to the disbelievers): "Tell me, if Allah took away your hearing and your sight, and sealed up your hearts, who is there - an ilah (a god) other than Allah who could restore them to you?" See how variously We explain the Ayat (proofs, evidence, verses, lessons, signs, revelations, etc.), yet they turn aside.

(27) And We shall turn their hearts and their eyes away (from guidance), as they refused to believe therein for the first time, and We shall leave them in their trespass to wander blindly.

(28) (And this is in order) that the hearts of those who disbelieve in the Hereafter may incline to such (deceit), and that they may remain pleased with it, and that they may commit what they are committing (all kinds of sins and evil deeds).

(29) Is it not clear to those who inherit the earth in succession from its (previous) possessors, that had We willed, We would have punished them for their sins. And We seal up their hearts so that they hear not?

(30) Those were the towns whose story We relate unto you (O Muhammad صلى الله عليه وسلم). And there came indeed to them their Messengers with clear proofs, but they were not such as to believe in that which they had rejected before. Thus Allah does seal up the hearts of the disbelievers (from every kind of religious guidance).