Musannaf Ibn Abi Shayba 13:1798

Abu Bakr narrated to us, he said: Waki’ narrated to us, he said: Ja’far ibn Burqan narrated to us, from al-Zuhri, from ‘Ubayd Allah ibn ‘Abd Allah ibn ‘Utbah, that Ibn Mas’ud bought a slave girl from his wife, Zaynab. She stipulated to him that if he were to sell her, she would have more right to her for the price. Ibn Mas’ud asked ‘Umar about it, and he disliked that he should have intercourse with her.