Musannaf Ibn Abi Shayba 13:2932

Abu Bakr narrated to us, he said: Ibn Abi Za’idah and Waki’ narrated to us, from Isma’il, from ‘Amir, who said: ‘Ali was approached regarding a certain matter—Waki’ said: regarding a thing—and he said: "It is indeed an injustice, and were it not that it is a settlement, I would have rejected it."