حَدَّثَنِي يَحْيَى، عَنْ مَالِكٍ، عَنْ نَافِعٍ، عَنْ عَبْدِ اللَّهِ بْنِ عُمَرَ، أَنَّ عُمَرَ بْنَ الْخَطَّابِ، قَالَ مَنْ بَاعَ عَبْدًا وَلَهُ مَالٌ فَمَالُهُ لِلْبَائِعِ إِلاَّ أَنْ يَشْتَرِطَهُ الْمُبْتَاعُ ‏.‏

Yahya related to me from Malik from Nafi from Abdullah ibn Umarthat Umar ibn al-Khattab said, "If a slave who has wealth is sold,that wealth belongs to the seller unless the buyer stipulates itsinclusion." Malik said, "The generally agreed upon way ofdoing things among us is that if the buyer stipulates the inclusion ofthe slave's property whether it be cash, debts, or goods of known orunknown value, then they belong to the buyer, even if the slavepossesses more than that for which he was purchased, whether he wasbought for cash, as payment for a debt, or in exchange for goods. Thisis possible because a master is not asked to pay zakat on his slave'sproperty. If a slave has a slave-girl, it is halal for him to haveintercourse with her by his right of possession. If a slave is freedor put under contract (kitaba) to purchase his freedom, then hisproperty goes with him. If he becomes bankrupt, his creditors take hisproperty and his master is not liable for any of his debts." Translation Not Available

Book reference: Muwatta Imam Malik Book 31 Hadith 1294
Web reference: Muwatta Imam Malik Book 31 Hadith 2