Sahih al-Bukhari 4499
Book 65: Prophetic Commentary on the Qur'an (Tafseer of the Prophet (pbuh)) · Narrated by Anas
Arabic
حَدَّثَنَا مُحَمَّدُ بْنُ عَبْدِ اللَّهِ الأَنْصَارِيُّ، حَدَّثَنَا حُمَيْدٌ، أَنَّ أَنَسًا، حَدَّثَهُمْ عَنِ النَّبِيِّ صلى الله عليه وسلم قَالَ " كِتَابُ اللَّهِ الْقِصَاصُ ".
English translation
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)
Reference: Sahih al-Bukhari 4499, Book of Prophetic Commentary on the Qur'an (Tafseer of the Prophet (pbuh)). English translation by Dr. Muhammad Muhsin Khan.