Al-Kahf - 18:22

سَيَقُولُونَ ثَلَاثَةٌ رَّابِعُهُمْ كَلْبُهُمْ وَيَقُولُونَ خَمْسَةٌ سَادِسُهُمْ كَلْبُهُمْ رَجْمًا بِالْغَيْبِ وَيَقُولُونَ سَبْعَةٌ وَثَامِنُهُمْ كَلْبُهُمْ قُل رَّبِّي أَعْلَمُ بِعِدَّتِهِم مَّا يَعْلَمُهُمْ إِلَّا قَلِيلٌ فَلَا تُمَارِ فِيهِمْ إِلَّا مِرَاء ظَاهِرًا وَلَا تَسْتَفْتِ فِيهِم مِّنْهُمْ أَحَدًا
[18:22]
(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.
(Some) say they were three, the dog being the fourth among them; (others) say they were five, the dog being the sixth,- doubtfully guessing at the unknown; (yet others) say they were seven, the dog being the eighth. Say thou: "My Lord knoweth best their number; It is but few that know their (real case)." Enter not, therefore, into controversies concerning them, except on a matter that is clear, nor consult any of them about (the affair of) the Sleepers.
(Some) will say: They were three, their dog the fourth, and (some) say: Five, their dog the sixth, guessing at random; and (some) say: Seven, and their dog the eighth. Say (O Muhammad): My Lord is Best Aware of their number. None knoweth them save a few. So contend not concerning them except with an outward contending, and ask not any of them to pronounce concerning them.