Surah Al-Kahf 18:26

قُلِ ٱللَّهُ أَعْلَمُ بِمَا لَبِثُوا۟ ۖ لَهُۥ غَيْبُ ٱلسَّمَـٰوَٰتِ وَٱلْأَرْضِ ۖ أَبْصِرْ بِهِۦ وَأَسْمِعْ ۚ مَا لَهُم مِّن دُونِهِۦ مِن وَلِىٍّ وَلَا يُشْرِكُ فِى حُكْمِهِۦٓ أَحَدًا

Say, "Allāh is most knowing of how long they remained. He has [knowledge of] the unseen [aspects] of the heavens and the earth. How Seeing is He and how Hearing! They have not besides Him any protector, and He shares not His legislation with anyone."

Translation: Saheeh International

Tafsir

Say ‘God is more knowledgeable of how long they tarried more knowledgeable than those contending over this issue — and this fact has already been mentioned above verse 19. To Him belongs the Unseen of the heavens and the earth that is to Him belongs the knowledge thereof. …

Excerpt from Tafsir al-Jalalayn, commentary on 18:26, via Quran.com. The reader has the full commentary and 9 more tafsirs.