Surah Al-An'am 6:23

ثُمَّ لَمْ تَكُن فِتْنَتُهُمْ إِلَّآ أَن قَالُوا۟ وَٱللَّهِ رَبِّنَا مَا كُنَّا مُشْرِكِينَ

Then there will be no [excuse upon] examination except they will say, "By Allāh, our Lord, we were not those who associated."

Translation: Saheeh International

Tafsir

Then their dissension read accusative fitnatahum or nominative fitnatuhum their apology was read lam takun or lam yakun only to say in other words was only their saying ‘By God our Lord read rabbinā as an adjective of wa’Llāhi ‘by God’ or rabbanā as a vocative we were never idolaters’.

Excerpt from Tafsir al-Jalalayn, commentary on 6:23, via Quran.com. The reader has the full commentary and 9 more tafsirs.