Narrated Jarir:
The Prophet said to me during Hajjat-al-Wida’: Let the people keep quiet and listen. Then he saidĀ (addressing the people), “Do not (become infidels) revert to disbelief after me by striking the necksĀ (cutting the throats) of one another (killing each other).”
Sahih Bukhari, Volume 1, Book3, Number 122