Narrated Hisham:My father told me that Hakim bin Hizam manumitted one-hundred slaves in the Pre-Islamic period of ignorance and slaughtered one-hundred camels (and distributed them in charity). When he embraced Islam he again slaughtered one-hundred camels and manumitted one-hundred slaves. Hakim said, "I asked Allah's Messenger (ﷺ), 'O Allah's Messenger (ﷺ)! What do you think about some good deeds I used to practice in the Pre-Islamic period of ignorance regarding them as deeds of righteousness?' Allah's Apostle said, "You have embraced Islam along with all those good deeds you did."
حَدَّثَنَا عُبَيْدُ بْنُ إِسْمَاعِيلَ، حَدَّثَنَا أَبُو أُسَامَةَ، عَنْ هِشَامٍ، أَخْبَرَنِي أَبِي أَنَّ حَكِيمَ بْنَ حِزَامٍ ـ رضى الله عنه ـ أَعْتَقَ فِي الْجَاهِلِيَّةِ مِائَةَ رَقَبَةٍ، وَحَمَلَ عَلَى مِائَةِ بَعِيرٍ، فَلَمَّا أَسْلَمَ حَمَلَ عَلَى مِائَةِ بَعِيرٍ وَأَعْتَقَ مِائَةَ رَقَبَةٍ، قَالَ فَسَأَلْتُ رَسُولَ اللَّهِ صلى الله عليه وسلم فَقُلْتُ يَا رَسُولَ اللَّهِ، أَرَأَيْتَ أَشْيَاءَ كُنْتُ أَصْنَعُهَا فِي الْجَاهِلِيَّةِ، كُنْتُ أَتَحَنَّثُ بِهَا، يَعْنِي أَتَبَرَّرُ بِهَا، قَالَ فَقَالَ رَسُولُ اللَّهِ صلى الله عليه وسلم " أَسْلَمْتَ عَلَى مَا سَلَفَ لَكَ مِنْ خَيْرٍ ".
Bukhari
Manumission of Slaves • Hadith 22