It is narrated from the father of Sayyiduna al-Hajjaj bin Malik al-Aslami (may Allah be pleased with him) that he asked the Prophet (peace and blessings be upon him): What is appropriate to give to discharge the obligation owed for suckling? So the Prophet (peace and blessings be upon him) said: "Something fine: a male slave or a female slave."
Hadith Referenceالمعجم الكبير للطبراني / باب الحاء / 3192