Hadith 1436

Narrated Hakim bin Hizam:

I said to Allah's Apostle, "Before embracing Islam I used to do good deeds like giving in charity, slave-manumitting, and the keeping of good relations with Kith and kin. Shall I be rewarded for those deeds?" The Prophet replied, "You became Muslim with all those good deeds (Without losing their reward)."

حَدَّثَنَا عَبْدُ اللَّهِ بْنُ مُحَمَّدٍ، حَدَّثَنَا هِشَامٌ، حَدَّثَنَا مَعْمَرٌ، عَنِ الزُّهْرِيِّ، عَنْ عُرْوَةَ، عَنْ حَكِيمِ بْنِ حِزَامٍ ـ رضى الله عنه ـ قَالَ قُلْتُ يَا رَسُولَ اللَّهِ أَرَأَيْتَ أَشْيَاءَ كُنْتُ أَتَحَنَّثُ بِهَا فِي الْجَاهِلِيَّةِ مِنْ صَدَقَةٍ أَوْ عَتَاقَةٍ وَصِلَةِ رَحِمٍ فَهَلْ فِيهَا مِنْ أَجْرٍ فَقَالَ النَّبِيُّ صلى الله عليه وسلم ‏"‏ أَسْلَمْتَ عَلَى مَا سَلَفَ مِنْ خَيْرٍ ‏"‏‏.‏

Reference: 113360
In-book reference: Book 24, Hadith 1436
Hadith 1436 - Obligatory Charity Tax (Zakat) - Sahih al-Bukhari - Sunnah.com