In the story of Barirah, she said, "Her husband was a slave, so the Messenger of Allah ﷺ gave her the choice, and she chose herself. Had he been free, he would not have given her the choice."
حدثنا عثمان بن أبي شيبة حدثنا جرير عن هشام بن عروة عن أبيه
في قصة بريرة قالت كان زوجها عبدا فخيرها رسول الله ﷺ فاختارت نفسها ولو كان حرا لم يخيرها
Muslim narrated it, Emancipation, chapter on the explanation that walaa (right of inheritance from a freed slave) belongs to the one who freed him, no. 9/1504, from the hadith of Jareer, and Bukhari, the Contracted Slave, chapter on the contracted slave seeking help and asking people, no. 2563, from the hadith of Hisham bin Urwa, through him, at length.The phrase "had he been free, he would not have given her the choice" is an insertion from the statement of Urwa, as the version of Nasai makes clear.