Ada' bin Khalid bin Hawdhah (may Allah be pleased with him) said: "Shall I not read to you a letter that the Messenger of Allah (peace and blessings be upon him) wrote for me?" He brought out a letter, and in it was: "This is what Ada' bin Khalid bin Hawdhah bought from Muhammad, the Messenger of Allah (peace and blessings be upon him): a male or a female slave (Abbad was unsure), with no disease, no deceit and no defect; it is the sale of a Muslim to a Muslim."
This hadith is known through Abbad bin al-Layth, and we have recorded it through another route that is not reliable.
Hadith Referenceالسنن الكبرى للبيهقي / كتاب البيوع / 10782