It was narrated from Anas that :
the Prophet (ﷺ) bought Safiyyah for seven slaves. (Sahih) (One of the narrators) 'Abdur-Rahman said: "From Dihyah Kalbi.' (IT)
English reference (IT): Vol. 3, Book 12, Hadith 2272 (IT)
Arabic reference (IT): Book 12, Hadith 2358 (IT)