Sahih al-Bukhari, Hadith 6921 ⓘ
Narrated Ibn Mas`ud: A man said, "O Allah's Messenger! Shall we be punished for what we did in the Prelslamic Period of ignorance?" The Prophet 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 " .
also referenced under: Book 88, Hadith 4 (In-Book) & Volume 9, Book 84, Hadith 56 (USC-MSA)