It was narrated that Rifa'ah bin Shaddad Al-Qitbani said:
"Were it not for a word that I heard from 'Amr bin Hamiq Khuza'i, I would have separated the head of Al-Mukhtar from his body. I heard him saying: "The Messenger of Allah (ﷺ) said: 'If a man trusts someone with his life then he kills him, he will carry a banner of treachery on the day of Resurrection.'"
English reference: Vol. 3, Book 21, Hadith 2688
Arabic reference: Book 21, Hadith 2790