(19) باب فِي الْمَمْلُوكَةِ تَعْتِقُ وَهِيَ تَحْتَ حُرٍّ أَوْ عَبْدٍ
Ibn 'Abbas said "The husband of Barirah was a black slave called Mughith. The Prophet (ﷺ) gave her choice and commanded her to observe the waiting period."
Reference: Sunan Abi Dawud 2232
In-book reference: Book 13, Hadith 58
English translation: Book 12, Hadith 2224