The word(s) "heart" appears 169 time(s) in 159 verse(s) in Quran in Muhammad Pickthal translation.

(11) If ye be on a journey and cannot find a scribe, then a pledge in hand (shall suffice). And if one of you entrusteth to another let him who is trusted deliver up that which is entrusted to him (according to the pact between them) and let him observe his duty to Allah his Lord. Hide not testimony. He who hideth it, verily his heart is sinful. Allah is Aware of what ye do.

(12) He it is Who hath revealed unto thee (Muhammad) the Scripture wherein are clear revelations - they are the substance of the Book - and others (which are) allegorical. But those in whose hearts is doubt pursue, forsooth, that which is allegorical seeking (to cause) dissension by seeking to explain it. None knoweth its explanation save Allah. And those who are of sound instruction say: We believe therein; the whole is from our Lord; but only men of understanding really heed.

(13) Our Lord! Cause not our hearts to stray after Thou hast guided us, and bestow upon us mercy from Thy Presence. Lo! Thou, only Thou, art the Bestower.

(14) And hold fast, all of you together, to the cable of Allah, and do not separate. And remember Allah's favour unto you: How ye were enemies and He made friendship between your hearts so that ye became as brothers by His grace; and (how) ye were upon the brink of an abyss of fire, and He did save you from it. Thus Allah maketh clear His revelations unto you, that haply ye may be guided,

(15) Allah ordained this only as a message of good cheer for you, and that thereby your hearts might be at rest - Victory cometh only from Allah, the Mighty, the Wise -

(16) We shall cast terror into the hearts of those who disbelieve because they ascribe unto Allah partners, for which no warrant hath been revealed. Their habitation is the Fire, and hapless the abode of the wrong-doers.

(17) Then, after grief, He sent down security for you. As slumber did it overcome a party of you, while (the other) party, who were anxious on their own account, thought wrongly of Allah, the thought of ignorance. They said: Have we any part in the cause? Say (O Muhammad): The cause belongeth wholly to Allah. They hide within themselves (a thought) which they reveal not unto thee, saying: Had we had any part in the cause we should not have been slain here. Say: Even though ye had been in your houses, those appointed to be slain would have gone forth to the places where they were to lie. (All this hath been) in order that Allah might try what is in your breasts and prove what is in your hearts. Allah is Aware of what is hidden in the breasts (of men).

(18) O ye who believe! Be not as those who disbelieved and said of their brethren who went abroad in the land or were fighting in the field: If they had been (here) with us they would not have died or been killed: that Allah may make it anguish in their hearts. Allah giveth life and causeth death; and Allah is Seer of what ye do.

(19) It was by the mercy of Allah that thou wast lenient with them (O Muhammad), for if thou hadst been stern and fierce of heart they would have dispersed from round about thee. So pardon them and ask forgiveness for them and consult with them upon the conduct of affairs. And when thou art resolved, then put thy trust in Allah. Lo! Allah loveth those who put their trust (in Him).

(20) And that He might know the hypocrites, unto whom it was said: Come, fight in the way of Allah, or defend yourselves. They answered: If we knew aught of fighting we would follow you. On that day they were nearer disbelief than faith. They utter with their mouths a thing which is not in their hearts. Allah is Best Aware of what they hide.