(2) باب الْقَسَامَةِ
It was narrated that Ibn Al-Musayyab said:
"Qasamah existed during the Jahiliyyah, then the Messenger of Allah confirmed it in the case of an Ansari who was found slain in the dry well of the jews, and Ansar said: "The Jews kill our companion."'
Reference: Sunan an-Nasa'i 4709
In-book reference: Book 45, Hadith 4
English translation: Vol. 5, Book 45, Hadith 4713