Sahih al-Bukhari 5169
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.‏