• خَمْسَة
• خَٰمِسَة
• خُمُسهُۥ
• خَمْسِين

Appears 8 times in the Quran.

1. 3:125 بَلَىٰٓ إِن تَصْبِرُوا۟ وَتَتَّقُوا۟ وَيَأْتُوكُم مِّن فَوْرِهِمْ هَٰذَا يُمْدِدْكُمْ رَبُّكُم بِخَمْسَةِ ءَالَٰفٍ مِّنَ ٱلْمَلَٰٓئِكَةِ مُسَوِّمِينَ

   Yea! if you remain patient and are on your guard, and they come upon you in a headlong manner, your Lord will assist you with five thousand of the havoc-making angels.
   

2. 8:41 وَٱعْلَمُوٓا۟ أَنَّمَا غَنِمْتُم مِّن شَىْءٍ فَأَنَّ لِلَّهِ خُمُسَهُۥ وَلِلرَّسُولِ وَلِذِى ٱلْقُرْبَىٰ وَٱلْيَتَٰمَىٰ وَٱلْمَسَٰكِينِ وَٱبْنِ ٱلسَّبِيلِ إِن كُنتُمْ ءَامَنتُم بِٱللَّهِ وَمَآ أَنزَلْنَا عَلَىٰ عَبْدِنَا يَوْمَ ٱلْفُرْقَانِ يَوْمَ ٱلْتَقَى ٱلْجَمْعَانِ وَٱللَّهُ عَلَىٰ كُلِّ شَىْءٍ قَدِيرٌ

   And know that whatever thing you gain, a fifth of it is for Allah and for the Messenger and for the near of kin and the orphans and the needy and the wayfarer, if you believe in Allah and in that which We revealed to Our servant, on the day of distinction, the day on which the two parties met; and Allah has power over all things.
   

3. 18:22 سَيَقُولُونَ ثَلَٰثَةٌ رَّابِعُهُمْ كَلْبُهُمْ وَيَقُولُونَ خَمْسَةٌ سَادِسُهُمْ كَلْبُهُمْ رَجْمًۢا بِٱلْغَيْبِ وَيَقُولُونَ سَبْعَةٌ وَثَامِنُهُمْ كَلْبُهُمْ قُل رَّبِّىٓ أَعْلَمُ بِعِدَّتِهِم مَّا يَعْلَمُهُمْ إِلَّا قَلِيلٌ فَلَا تُمَارِ فِيهِمْ إِلَّا مِرَآءً ظَٰهِرًا وَلَا تَسْتَفْتِ فِيهِم مِّنْهُمْ أَحَدًا

   (Some) say: (They are) three, the fourth of them being their dog; and (others) say: Five, the sixth of them being their dog, making conjectures at what is unknown; and (others yet) say: Seven, and the eighth of them is their dog. Say: My Lord best knows their number, none knows them but a few; therefore contend not in the matter of them but with an outward contention, and do not question concerning them any of them.
   

4. 24:7 وَٱلْخَٰمِسَةُ أَنَّ لَعْنَتَ ٱللَّهِ عَلَيْهِ إِن كَانَ مِنَ ٱلْكَٰذِبِينَ

   And the fifth (time) that the curse of Allah be on him if he is one of the liars.
   

5. 24:9 وَٱلْخَٰمِسَةَ أَنَّ غَضَبَ ٱللَّهِ عَلَيْهَآ إِن كَانَ مِنَ ٱلصَّٰدِقِينَ

   And the fifth (time) that the wrath of Allah be on her if he is one of the truthful.
   

6. 29:14 وَلَقَدْ أَرْسَلْنَا نُوحًا إِلَىٰ قَوْمِهِۦ فَلَبِثَ فِيهِمْ أَلْفَ سَنَةٍ إِلَّا خَمْسِينَ عَامًا فَأَخَذَهُمُ ٱلطُّوفَانُ وَهُمْ ظَٰلِمُونَ

   And certainly We sent Nuh to his people, so he remained among them a thousand years save fifty years. And the deluge overtook them, while they were unjust.
   

7. 58:7 أَلَمْ تَرَ أَنَّ ٱللَّهَ يَعْلَمُ مَا فِى ٱلسَّمَٰوَٰتِ وَمَا فِى ٱلْأَرْضِ مَا يَكُونُ مِن نَّجْوَىٰ ثَلَٰثَةٍ إِلَّا هُوَ رَابِعُهُمْ وَلَا خَمْسَةٍ إِلَّا هُوَ سَادِسُهُمْ وَلَآ أَدْنَىٰ مِن ذَٰلِكَ وَلَآ أَكْثَرَ إِلَّا هُوَ مَعَهُمْ أَيْنَ مَا كَانُوا۟ ثُمَّ يُنَبِّئُهُم بِمَا عَمِلُوا۟ يَوْمَ ٱلْقِيَٰمَةِ إِنَّ ٱللَّهَ بِكُلِّ شَىْءٍ عَلِيمٌ

   Do you not see that Allah knows whatever is in the heavens and whatever is in the earth? Nowhere is there a secret counsel between three persons but He is the fourth of them, nor (between) five but He is the sixth of them, nor less than that nor more but He is with them wheresoever they are; then He will inform them of what they did on the day of resurrection: surely Allah is Cognizant of all things.
   

8. 70:4 تَعْرُجُ ٱلْمَلَٰٓئِكَةُ وَٱلرُّوحُ إِلَيْهِ فِى يَوْمٍ كَانَ مِقْدَارُهُۥ خَمْسِينَ أَلْفَ سَنَةٍ

   To Him ascend the angels and the Spirit in a day the measure of which is fifty thousand years.