Surah Al-An'am 6:31

قَدْ خَسِرَ ٱلَّذِينَ كَذَّبُوا۟ بِلِقَآءِ ٱللَّهِ ۖ حَتَّىٰٓ إِذَا جَآءَتْهُمُ ٱلسَّاعَةُ بَغْتَةً قَالُوا۟ يَـٰحَسْرَتَنَا عَلَىٰ مَا فَرَّطْنَا فِيهَا وَهُمْ يَحْمِلُونَ أَوْزَارَهُمْ عَلَىٰ ظُهُورِهِمْ ۚ أَلَا سَآءَ مَا يَزِرُونَ

Those will have lost who deny the meeting with Allāh, until when the Hour [of resurrection] comes upon them unexpectedly, they will say, "Oh, [how great is] our regret over what we neglected concerning it [i.e., the Hour]," while they bear their burdens [i.e., sins] on their backs. Unquestionably, evil is that which they bear.

Translation: Saheeh International

Tafsir

They indeed are losers who deny the encounter with God through resurrection until hattā is purposive to expose the extent of their mendacity when the Hour the Resurrection comes upon them suddenly they shall say ‘Alas for us yā hasratanā ‘O grief of ours’ expresses extreme suffering the vocative call to which is …

Excerpt from Tafsir al-Jalalayn, commentary on 6:31, via Quran.com. The reader has the full commentary and 9 more tafsirs.