Musannaf Ibn Abi Shayba 38:17

Ghundar narrated to us, from Shu'bah, from Sa'd ibn Ibrahim, who said: I heard my father say: It reached Ali ibn Abi Talib that Talhah says, "I only pledged allegiance while my neck was turned away." He said: So he sent Ibn Abbas, and he asked them. He said: Usamah ibn Zayd said, "As for his neck being turned away, I do not know of it, but he did pledge allegiance while he was reluctant." He said: Then the people leaped toward him until they almost killed him. He said: So Suhayb went out, and I was at his side. He turned to me and said, "I thought that Umm 'Awf was enraged."