It is reported about Sayyiduna Abdullah bin Salam (may Allah be pleased with him) that when the people rose in agitation over the matter of Sayyiduna Uthman (may Allah be pleased with him), he said: O people! Do not kill this elder; seek to have him make amends, for whenever a nation killed its prophet, its affairs were not set right until the blood of seventy thousand of them had been shed, and whenever a nation killed its prophet's caliph, its affairs were not set right until the blood of forty thousand of them had been shed. But the people paid no attention to what he said, and they killed him (Sayyiduna Uthman). Once he sat on the road waiting for Sayyiduna Ali (may Allah be pleased with him) and asked Sayyiduna Ali (may Allah be pleased with him): Where do you intend to go? He said: I wish to go to the land of Iraq. Sayyiduna Abdullah bin Salam (may Allah be pleased with him) said: Do not go to Iraq; keep to the pulpit of the Messenger of Allah. Some of Sayyiduna Ali's (may Allah be pleased with him) companions began to set upon him, and Sayyiduna Ali (may Allah be pleased with him) said: Leave him, for he is one of us, the People of the House. When Sayyiduna Ali (may Allah be pleased with him) was martyred, Sayyiduna Abdullah bin Salam (may Allah be pleased with him) said to Ibn Ma'qil: This is the year forty, and at its turn there will be a peace settlement. Whenever a nation killed its prophet, seventy thousand were killed in return for him, and whenever a nation killed its prophet's caliph, forty thousand were killed in return for him.
Al-Tabarani recorded it through two chains, and the narrators of this one are the narrators of the Sahih. It has another chain that will come in the chapter on the virtues of Sayyiduna Uthman (may Allah be pleased with him).
Hadith Referenceمجمع الزوائد ومنبع الفوائد / كتاب الفتن - أعاذنا الله منها / 12073