Sahih al-Bukhari 6921
Narrated Ibn Mas`ud:
A man said, "O Allah's Messenger (ﷺ)! Shall we be punished for what we did in the Prelslamic Period of 
ignorance?" The Prophet (ﷺ) said, "Whoever does good in Islam will not be punished for what he did in 
the Pre-lslamic Period of ignorance and whoever does evil in Islam will be punished for his former 
and later (bad deeds).
حَدَّثَنَا خَلاَّدُ بْنُ يَحْيَى، حَدَّثَنَا سُفْيَانُ، عَنْ مَنْصُورٍ، وَالأَعْمَشِ، عَنْ أَبِي وَائِلٍ، عَنِ ابْنِ مَسْعُودٍ ـ رضى الله عنه ـ قَالَ قَالَ رَجُلٌ يَا رَسُولَ اللَّهِ أَنُؤَاخَذُ بِمَا عَمِلْنَا فِي الْجَاهِلِيَّةِ قَالَ ‏
"‏ مَنْ أَحْسَنَ فِي الإِسْلاَمِ لَمْ يُؤَاخَذْ بِمَا عَمِلَ فِي الْجَاهِلِيَّةِ، وَمَنْ أَسَاءَ فِي الإِسْلاَمِ أُخِذَ بِالأَوَّلِ وَالآخِرِ ‏"‏‏.‏