Hadithcore
Sahih al-Bukhari, 5169
sahih

Narrated Anas:

Allah's Messenger (ﷺ) manumitted Safiyya and then married her, and her Mahr was her manumission, and he gave a wedding banquet with Hais (a sort of sweet dish made from butter, cheese and dates).

حَدَّثَنَا مُسَدَّدٌ، عَنْ عَبْدِ الْوَارِثِ، عَنْ شُعَيْبٍ، عَنْ أَنَسٍ، أَنَّ رَسُولَ اللَّهِ صلى الله عليه وسلم أَعْتَقَ صَفِيَّةَ، وَتَزَوَّجَهَا وَجَعَلَ عِتْقَهَا صَدَاقَهَا، وَأَوْلَمَ عَلَيْهَا بِحَيْسٍ‏.‏

References2 variants
In-Book Reference
Book 67, Hadith 104
USC-MSA web (English) reference
Vol. 7, Book 62, Hadith 98 (deprecated numbering scheme)