It was narrated that Anas said:“Safiyyah was given to Dihyah Al-Kalbi (as his share of the war booty), then she was given to the Messenger of Allah after that. He married her, and made her ransom (i.e., freedom from slavery) her dowry.” (Sahih)Hammad said: “Abdul-'Aziz said to Thabit: 'O Abu Muhammad! Did you ask Anas what her bridal-money was?' He said: 'Her bridal-money was her freedom.' ”
حَدَّثَنَا أَحْمَدُ بْنُ عَبْدَةَ، حَدَّثَنَا حَمَّادُ بْنُ زَيْدٍ، حَدَّثَنَا ثَابِتٌ، وَعَبْدُ الْعَزِيزِ، عَنْ أَنَسٍ، قَالَ صَارَتْ صَفِيَّةُ لِدِحْيَةَ الْكَلْبِيِّ ثُمَّ صَارَتْ لِرَسُولِ اللَّهِ ـ صلى الله عليه وسلم ـ بَعْدُ فَتَزَوَّجَهَا وَجَعَلَ عِتْقَهَا صَدَاقَهَا . قَالَ حَمَّادٌ فَقَالَ عَبْدُ الْعَزِيزِ لِثَابِتٍ يَا أَبَا مُحَمَّدٍ أَنْتَ سَأَلْتَ أَنَسًا مَا أَمْهَرَهَا قَالَ أَمْهَرَهَا نَفْسَهَا .
IbnMaja
The Chapters on Marriage • Hadith 1957