Sahih al-Bukhari 4201Book 64, Hadith 241
حَدَّثَنَا آدَمُ، حَدَّثَنَا شُعْبَةُ، عَنْ عَبْدِ الْعَزِيزِ بْنِ صُهَيْبٍ، قَالَ سَمِعْتُ أَنَسَ بْنَ مَالِكٍ ـ رضى الله عنه ـ يَقُولُ سَبَى النَّبِيُّ صلى الله عليه وسلم صَفِيَّةَ، فَأَعْتَقَهَا وَتَزَوَّجَهَا. فَقَالَ ثَابِتٌ لأَنَسٍ مَا أَصْدَقَهَا قَالَ أَصْدَقَهَا نَفْسَهَا فَأَعْتَقَهَا.
Anas bin Malik said, "The Prophet (ﷺ) took Safiya as a captive. He manumitted her and married her." Thabit asked Anas, "What did he give her as Mahr (i.e. marriage gift)?" Anas replied. "Her Mahr was herself, for he manumitted her."