مُسْنَدُ أَحْمَدَ
Musnad Ahmad 1427
The Musnad of az-Zubair bin al-'Awwam
Al-Hasan said: A man came to az-Zubair bin al-"Awwam (رضي الله عنه) and said: “Shall I not kill "Ali for you?” He said: “How can you kill him when he has people with him?” (and he narrated a similar report.)
Musnad Ahmad 1427Sahih]