Safiyyah was first allotted to Dihya Kalbi, then she came to the Messenger of Allah ﷺ, who married her and made her freedom her dowry.Hammad said that Abdul-Aziz asked Thabit, "Abu Muhammad, did you yourself ask Anas what he gave her as her dowry?"Thabit replied, "He gave her her own self as her dowry."
حدثنا أحمد بن عبدة حدثنا حماد بن زيد حدثنا ثابت وعبد العزيز
صارت صفية لدحية الكلبي ثم صارت لرسول الله ﷺ بعد فتزوجها وجعل عتقها صداقها قال حماد فقال عبد العزيز لثابت يا أبا محمد أنت سألت أنسا ما أمهرها قال أمهرها نفسها
Bukhari narrated it in the chapter on the prayer of fear, in the section on takbir and praying dawn in the dark and prayer during a raid or battle, hadith 947 (in full) and 5086, and Muslim narrated it in the chapter on marriage, in the section on the merit of freeing one's slave woman and then marrying her, hadith 1365, from the hadith of Hammad bin Zayd, with this wording.