Musannaf Ibn Abi Shayba 13:2437

Abu Bakr narrated to us, he said: Abd al-Salam narrated to us, from Isma'il ibn 'Abd al-Malik, that a woman died and left behind a young child and a slave girl. The father wanted to buy the slave girl. Sa'id said: "Have her appraised in the market for a value, then bear witness against yourself for her price, then do with her whatever seems good to you."