Sahih Bukhari
Blood Money (Ad-Diyat)
Volume: 009 / Book Number: 083 / Hadith Number: 8
Narrated Abu Zur'a bin 'Amr bin Jarir:
The Prophet said during Hajjat-al-Wada', "Let the people be quiet and listen to me. After me, do not become disbelievers, by striking (cutting) the necks of one another."