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.' (ID)
English reference (ID): Vol. 3, Book 12, Hadith 2272 (ID)
Arabic reference (ID): Book 12, Hadith 2358 (ID)