Appears 3 times in the Quran.
18:18 وَتَحْسَبُهُمْ أَيْقَاظًا وَهُمْ رُقُودٌ وَنُقَلِّبُهُمْ ذَاتَ ٱلْيَمِينِ وَذَاتَ ٱلشِّمَالِ وَكَلْبُهُم بَٰسِطٌ ذِرَاعَيْهِ بِٱلْوَصِيدِ لَوِ ٱطَّلَعْتَ عَلَيْهِمْ لَوَلَّيْتَ مِنْهُمْ فِرَارًا وَلَمُلِئْتَ مِنْهُمْ رُعْبًا
And you might think them awake while they were asleep and We turned them about to the right and to the left, while their dog (lay) outstretching its paws at the entrance; if you looked at them you would certainly turn back from them in flight, and you would certainly be filled with awe because of them.
On them is fire closed over.
Surely it shall be closed over upon them,