The Messenger of Allah ﷺ said to us, "If any of you has a slave who has contracted to buy his freedom, and he possesses enough to pay off his contract, she should observe veiling from him."
حدثنا مسدد بن مسرهد حدثنا سفيان عن الزهري عن نبهان مكاتب أم سلمة قال سمعت
قال لنا رسول الله ﷺ إن كان لإحداكن مكاتب فكان عنده ما يؤدي فلتحتجب منه
Its chain is hasan. Tirmidhi narrated it in the Book of Business Transactions, chapter on what has been mentioned regarding a slave under a contract of manumission when he has enough to pay it off, hadith no. 1261, and Ibn Majah narrated it, hadith no. 2520, from the hadith of Sufyan bin Uyayna, with the same chain. Tirmidhi said, "Hasan sahih." Ibn Hibban graded it sahih, hadith no. 1214, as did Hakim, 20/219, and Dhahabi agreed with him. Nabhan is hasan al-hadith according to the more correct view, see hadith no. 4112.