Sunan of Abu Dawood Book 13, Hadith 2233

حَدَّثَنَا عُثْمَانُ بْنُ أَبِي شَيْبَةَ، حَدَّثَنَا جَرِيرٌ، عَنْ هِشَامِ بْنِ عُرْوَةَ، عَنْ أَبِيهِ، عَنْ عَائِشَةَ، فِي قِصَّةِ بَرِيرَةَ قَالَتْ كَانَ زَوْجُهَا عَبْدًا فَخَيَّرَهَا رَسُولُ اللَّهِ صلى الله عليه وسلم فَاخْتَارَتْ نَفْسَهَا وَلَوْ كَانَ حُرًّا لَمْ يُخَيِّرْهَا ‏.‏

While relating the tradition about Barirah A'ishah said "her husband was a slave, so the Prophet(ﷺ) gave her choice. She chose herself. Had he been a free man, he would not given her choice."