Barirah's husband was a free man, so the Messenger of Allah ﷺ gave her the choice.
حدثنا هناد حدثنا أبو معاوية عن الأعمش عن إبراهيم عن الأسود
كان زوج بريرة حرا فخيرها رسول الله ﷺ
[Its chain of transmission is daif]Abu Dawud narrated it in his chapter on divorce, the section on one who said he was free, hadith 2235, from the narration of Ibrahim Nakhai with this wording, but I did not find explicit mention that he heard it directly. The narrator's statement, "Bariah's husband was free," is the statement of Aswad, may Allah have mercy on him. Ibn Hibban said in al-Ihsan, 4257, that Aswad was mistaken in his statement, "He was free."