Surah Al-Ahqaf 46:14

أُو۟لَـٰٓئِكَ أَصْحَـٰبُ ٱلْجَنَّةِ خَـٰلِدِينَ فِيهَا جَزَآءًۢ بِمَا كَانُوا۟ يَعْمَلُونَ

Those are the companions of Paradise, abiding eternally therein as reward for what they used to do.

Translation: Saheeh International

Tafsir

Those will be the inhabitants of Paradise abiding therein khālidīna fīhā is a circumstantial qualifier as a reward jazā’an is in the accusative as a verbal noun because of the implied verbal action that is to say yujzawna ‘they will be rewarded’ for what they used to do.

Excerpt from Tafsir al-Jalalayn, commentary on 46:14, via Quran.com. The reader has the full commentary and 9 more tafsirs.