Sahih Bukhari Volume 2, Book 24, Hadith Number 517.

Narated By 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).”