Musannaf Ibn Abi Shayba 13:1795

Abu Bakr narrated to us, he said: Ibn Abi Za’idah narrated to us, from Isma’il ibn Abi Khalid, from al-Sha’bi, regarding a man who buys a slave girl on the condition that he does not sell her, nor give her away, nor give her as a dowry. He said: "I wish I had found her and bought her with this condition, and stipulated for them that she is free when I die."