Narrated Anas:
The Prophet (ﷺ) said, "The prescribed Law of Allah is the equality in punishment (i.e. Al-Qisas)." (In cases of murders, etc.) (JA)
USC-MSA web (English) reference: Vol. 6, Book 60, Hadith 26 (JA)
Arabic reference (JA): Book 65, Hadith 4499 (JA)