Surah Al-Mu'minun 23:100

لَعَلِّىٓ أَعْمَلُ صَـٰلِحًا فِيمَا تَرَكْتُ ۚ كَلَّآ ۚ إِنَّهَا كَلِمَةٌ هُوَ قَآئِلُهَا ۖ وَمِن وَرَآئِهِم بَرْزَخٌ إِلَىٰ يَوْمِ يُبْعَثُونَ

That I might do righteousness in that which I left behind." No! It is only a word he is saying; and behind them is a barrier until the Day they are resurrected.

Translation: Saheeh International

Tafsir

that I might act righteously by witnessing that ‘there is no god but God’ that this might be in that which I have left behind’ in what I have wasted of my life in other words that this affirmation might be in its place. God exalted be He says By no means! that is there shall be no return. …

Excerpt from Tafsir al-Jalalayn, commentary on 23:100, via Quran.com. The reader has the full commentary and 9 more tafsirs.