Hajjaj bin Hajjaj al-Aslami (may Allah be pleased with him) narrates from his father that he said: I said: "O Messenger of Allah (peace and blessings be upon him), what will remove from me the obligation (owed) for nursing?" The Messenger of Allah (peace and blessings be upon him) said: "A white male slave or a white female slave." Abu Mu'awiyah (may Allah have mercy on him) and Abdullah bin Idris (may Allah have mercy on him) narrated it likewise from Hisham bin Urwah (may Allah have mercy on him), except that they both said: "A male slave or a female slave." It has been said: from Urwah (may Allah have mercy on him), from Hajjaj bin Hajjaj bin Malik (may Allah be pleased with him), from the Prophet (peace and blessings be upon him); and it has been said: from Urwah (may Allah have mercy on him), from Hajjaj bin Abi al-Hajjaj, from his father. What is correct is "Hajjaj bin Hajjaj, from his father"; Imam Bukhari (may Allah have mercy on him) said this.
Hadith Referenceالسنن الكبرى للبيهقي / كتاب الرضاع / 15678