Sahih al-Bukhari 4499
Sahih al-Bukhari · Book 65: Prophetic Commentary on the Qur'an (Tafseer of the Prophet (pbuh)) · "O you who believe! Al- Qisas (the Law of Equality in punishment) is prescribed for you..." (V.2:178)
Narrated Anas:
حَدَّثَنَا مُحَمَّدُ بْنُ عَبْدِ اللَّهِ الأَنْصَارِيُّ ، حَدَّثَنَا حُمَيْدٌ ، أَنَّ أَنَسًا ، حَدَّثَهُمْ عَنِ النَّبِيِّ صلى الله عليه وسلم قَالَ " كِتَابُ اللَّهِ الْقِصَاصُ " .
The Prophet (ﷺ) said, "The prescribed Law of Allah is the equality in punishment (i.e. Al-Qisas)." (In cases of murders, etc.)