The root م ح ص (m-ḥ-ṣ) in the Quran

وَلِيُمَحِّصَ ٱللَّهُ ٱلَّذِينَ ءَامَنُوا۟ وَيَمْحَقَ ٱلْكَٰفِرِينَ ۝١٤١

And that Allāh may purify the believers [through trials] and destroy the disbelievers.

ثُمَّ أَنزَلَ عَلَيْكُم مِّنۢ بَعْدِ ٱلْغَمِّ أَمَنَةً نُّعَاسًا يَغْشَىٰ طَآئِفَةً مِّنكُمْ وَطَآئِفَةٌ قَدْ أَهَمَّتْهُمْ أَنفُسُهُمْ يَظُنُّونَ بِٱللَّهِ غَيْرَ ٱلْحَقِّ ظَنَّ ٱلْجَٰهِلِيَّةِ يَقُولُونَ هَل لَّنَا مِنَ ٱلْأَمْرِ مِن شَىْءٍ قُلْ إِنَّ ٱلْأَمْرَ كُلَّهُۥ لِلَّهِ يُخْفُونَ فِىٓ أَنفُسِهِم مَّا لَا يُبْدُونَ لَكَ يَقُولُونَ لَوْ كَانَ لَنَا مِنَ ٱلْأَمْرِ شَىْءٌ مَّا قُتِلْنَا هَٰهُنَا قُل لَّوْ كُنتُمْ فِى بُيُوتِكُمْ لَبَرَزَ ٱلَّذِينَ كُتِبَ عَلَيْهِمُ ٱلْقَتْلُ إِلَىٰ مَضَاجِعِهِمْ وَلِيَبْتَلِىَ ٱللَّهُ مَا فِى صُدُورِكُمْ وَلِيُمَحِّصَ مَا فِى قُلُوبِكُمْ وَٱللَّهُ عَلِيمٌۢ بِذَاتِ ٱلصُّدُورِ ۝١٥٤

Then after distress, He sent down upon you security [in the form of] drowsiness, overcoming a faction of you, while another faction worried about themselves, thinking of Allāh other than the truth - the thought of ignorance, saying, "Is there anything for us [to have done] in this matter?" Say, "Indeed, the matter belongs completely to Allāh." They conceal within themselves what they will not reveal to you. They say, "If there was anything we could have done in the matter, we [i.e., some of us] would not have been killed right here." Say, "Even if you had been inside your houses, those decreed to be killed would have come out to their death beds." [It was] so that Allāh might test what is in your breasts and purify what is in your hearts. And Allāh is Knowing of that within the breasts.