The word(s) "hardened" appears 5 time(s) in 5 verse(s) in Quran in Mohsin Khan translation.

(1) Then, after that, your hearts were hardened and became as stones or even worse in hardness. And indeed, there are stones out of which rivers gush forth, and indeed, there are of them (stones) which split asunder so that water flows from them, and indeed, there are of them (stones) which fall down for fear of Allah. And Allah is not unaware of what you do.

(2) 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.

(3) That He (Allah) may make what is thrown in by Shaitan (Satan) a trial for those in whose hearts is a disease (of hypocrisy and disbelief) and whose hearts are hardened. And certainly, the Zalimun (polytheists and wrong-doers) are in an opposition far-off (from the truth against Allah's Messenger and the believers).

(4) Is he whose breast Allah has opened to Islam, so that he is in light from His Lord (as he who is a non-Muslim)? So woe to those whose hearts are hardened against remembrance of Allah! They are in plain error!

(5) Has not the time come for the hearts of those who believe (in the Oneness of Allah - Islamic Monotheism) to be affected by Allah's Reminder (this Qur'an), and that which has been revealed of the truth, lest they become as those who received the Scripture [the Taurat (Torah) and the Injeel (Gospel)] before (i.e. Jews and Christians), and the term was prolonged for them and so their hearts were hardened? And many of them were Fasiqun (the rebellious, the disobedient to Allah).