مُسْنَدُ أَحْمَدَ
Musnad Ahmad 1433
The Musnad of az-Zubair bin al-'Awwam
It was narrated that al-Hasan said: A man said to az-Zubair: “Shall I kill "Ali for you?” He said: “How would you kill him?” He said: “I will assassinate him.”He said: “No, the Messenger of Allah (ﷺ) said: Faith prohibits assassination; no believer should resort to that."
Musnad Ahmad 1433Sahih]