The word(s) "heart" appears 171 time(s) in 159 verse(s) in Quran in Muhammad Habib Shakir translation.

(131) When those who disbelieved harbored in their hearts (feelings of) disdain, the disdain of (the days of) ignorance, but Allah sent down His tranquillity on His Apostle and on the believers, and made them keep the word of guarding (against evil), and they were entitled to it and worthy of it; and Allah is Cognizant of all things.

(132) Muhammad is the Apostle of Allah, and those with him are firm of heart against the unbelievers, compassionate among themselves; you will see them bowing down, prostrating themselves, seeking grace from Allah and pleasure; their marks are in their faces because of the effect of prostration; that is their description in the Taurat and their description in the Injeel; like as seed-produce that puts forth its sprout, then strengthens it, so it becomes stout and stands firmly on its stem, delighting the sowers that He may enrage the unbelievers on account of them; Allah has promised those among them who believe and do good, forgiveness and a great reward.

(133) Surely those who lower their voices before Allah's Apostle are they whose hearts Allah has proved for guarding (against evil); they shall have forgiveness and a great reward.

(134) And know that among you is Allah's Apostle; should he obey you in many a matter, you would surely fall into distress, but Allah has endeared the faith to you and has made it seemly in your hearts, and He has made hateful to you unbelief and transgression and disobedience; these it is that are the followers of a right way.

(135) The dwellers of the desert say: We believe. Say: You do not believe but say, We submit; and faith has not yet entered into your hearts; and if you obey Allah and His Apostle, He will not diminish aught of your deeds; surely Allah is Forgiving, Merciful.

(136) Who fears the Beneficent Allah in secret and comes with a penitent heart:

(137) Most surely there is a reminder in this for him who has a heart or he gives ear and is a witness.

(138) The heart was not untrue in (making him see) what he saw.

(139) He causes the night to enter in upon the day, and causes the day to enter in upon the night, and He is Cognizant of what is in the hearts.

(140) Has not the time yet come for those who believe that their hearts should be humble for the remembrance of Allah and what has come down of the truth? And that they should not be like those who were given the Book before, but the time became prolonged to them, so their hearts hardened, and most of them are transgressors.