Hadith: The Messenger of Allah (may Allah's peace and blessings be upon him) emancipated Safiyyah and made her emancipation her dowry

عن أنس بن مالك رضي الله عنه أن رسول الله صلى الله عليه وسلم أعتق صفية، وجعل عِتْقَهَا صَدَاقَهَا.
[صحيح] - [متفق عليه]

Anas ibn Mālik (may Allah be pleased with him) reported that the Messenger of Allah (may Allah's peace and blessings be upon him) emancipated Safiyyah and made her emancipation her dowry.
Sahih/Authentic. - [Al-Bukhari and Muslim]

Explanation

Safiyyah, the daughter of Huyai, one of the leaders of Banu An-Nadīr (a Jewish tribe of Hejaz) was the wife of Kinānah ibn Abu Al-Huqayq who was killed on the Day of khaybar. The Prophet (may Allah's peace and blessings be upon him) conquered Khaybar without hostilities and the women and children residents of that city became slaves to the Muslims once they were captivated. Safiyyah was initially part of the share allocated to Dihyah ibn Khalīfah al-Kalbi. However, the Prophet (may Allah's peace and blessings be upon him) compensated him with another female slave in exchange for Safiyyah, and took her for himself. He did this to appease her and soothe her grief for her lost status and glory (may Allah's peace and blessings be upon him). The Prophet's noble character is manifested through the fact that he did not settle for enjoying her while she was a humiliated as a slave but freed her from slavery, raised her status, and made her one of the most respected of women (on earth as a) Mother of the Believers. He freed her, then married her, and he made her emancipation her dowry.