It was narrated that Muhammad bin ‘Ali said:
Some people came to `Ali (رضي الله عنه) and complained about `Uthman`s tax collector. My father said to me: take this letter to `Uthman (رضي الله عنه) and tell him: The people are complaining about your tax collector, and this is the instruction of the Messenger of Allah (ﷺ) about collecting zakah, tell them to follow it. So I went to `Uthman and told him about that, He (the narrator) said: If he [`Ali] had wanted to say anything about `Uthman, he would have said it on that occasion - i.e., saying something bad.