Sahih Bukhari Volume 9, Book 88, Hadith 6923

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 ‏"‏‏

Narrated By Ibn Mas'ud : A man said, "O Allah's Apostle! Shall we be punished for what we did in the Pre-Islamic Period of ignorance?" The Prophet said, "Whoever does good in Islam will not be punished for what he did in the Pre-Islamic Period of ignorance and whoever does evil in Islam will be punished for his former and later (bad deeds)."