Surah Al-Kahf 18:3
مَّـٰكِثِينَ فِيهِ أَبَدًا
In which they will remain forever
Translation: Saheeh International
Tafsir
wherein they will abide forever and this reward is Paradise;
Excerpt from Tafsir al-Jalalayn, commentary on 18:3, via Quran.com. The reader has the full commentary and 9 more tafsirs.