Sahih al-Bukhari 4201
Sahih al-Bukhari · Book 64: Military Expeditions led by the Prophet (pbuh) (Al-Maghaazi) · Ghazwa of Khaibar
Narrated `Abdul `Aziz bin Suhaib:
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."