I know of no proponent of this view among the followers of the four Imams or their counterparts among Ahl al-Sunnah. Rather, it is the view of many Marwānids (1) and those who agreed with them.
Among them are some who say that ʿAlī (2) was complicit in shedding ʿUthmān’s blood. Some say that he (3) gave the order openly; others say that he (4) gave it secretly; still others say that he approved of his killing and rejoiced at it; and yet others make different claims. All of this is falsehood and fabrication against ʿAlī—may Allah be pleased with him—(5). ʿAlī—may Allah be pleased with him—had no part (6) in ʿUthmān’s bloodshed; he neither ordered it nor approved of it.
It is related that he—and he was truthful and righteous (7)—said:
“By Allah, I did not kill ʿUthmān, nor did I assist in his killing.”
It is also related that he said:
“I neither killed him nor approved of his killing.”
It is further related that he heard Muʿāwiya’s supporters cursing ʿUthmān’s killers, whereupon he said:
“O Allah, curse ʿUthmān’s killers on land and sea, on plain and mountain.”
It is also related that some people (8) gave false testimony against him before the people of Syria, claiming that he had participated in shedding ʿUthmān’s blood (9). This was among the reasons that led them to withhold their allegiance from him: they believed that he was an oppressor, that he (10) was one of ʿUthmān’s killers, and that he had sheltered ʿUthmān’s killers because he agreed with them concerning his killing.