Sahih al-Bukhari, Hadith 4201 ⓘ
Narrated `Abdul `Aziz bin Suhaib: Anas bin Malik said, "The Prophet 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."
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.
also referenced under: Book 64, Hadith 241 (In-Book) & Volume 5, Book 59, Hadith 513 (USC-MSA)