What are the best books regarding the discord that arose among the Companions?

Question:
Many books have appeared that discuss the fitnah (trial, discord or temptation) that occurred among the Companions during the periods of the two Rightly Guided Caliphs, Uthman and Ali (may Allah be pleased with them all). We ask your Eminence to guide us to the best books that discuss this topic and contain nothing in their pages of lying or fabrication.

Answer:
We guide you to "Al-Aqidah al-Wasitiyyah," the most concise book; it is a brief book that is excellent and beneficial. Otherwise, there are lengthy books, but "Al-Aqidah al-Wasitiyyah" by Shaykh al-Islam Ibn Taymiyyah is a concise, beneficial, and sound book. In it, he (peace and blessings be upon him) said: "And they [the people of the Sunnah and the community] hold back from what arose among the Companions, and they say: 'Indeed, among the reports narrated regarding their faults, some are lies, and some have been added to, subtracted from, or altered from their original form. As for what is preserved of it, they were exercising independent legal reasoning (ijtihad) in it: either they were exercising independent legal reasoning and were correct, in which case they have two rewards, or they were mistaken, in which case they have one reward, and the mistake is forgiven.'"
This is the ruling regarding the fitnah (trial, discord or temptation): they were exercising independent legal reasoning (ijtihad), may Allah be pleased with them and grant them satisfaction. However, some of the transmission contains evil; some of the transmission from some of the weak transmitters conveys things that are not authentic. But as for what is established of their actions... whoever was correct has two rewards, and whoever was mistaken has one reward.
The people of the Sunnah say: Ali and his companions were the ones who were right, and Mu'awiyah made a mistake. Mu'awiyah's action was an act of armed rebellion against legitimate authority, but he was exercising independent legal reasoning; he was demanding the blood of those who killed Uthman. So he exercised independent legal reasoning and made a mistake, and he has the reward for his effort. The Prophet (peace and blessings be upon him) called him a rebel, saying regarding 'Amir: , and they were Mu'awiyah and his companions who killed him. So Ali and his companions are the people of justice, and they have the valid pledge of allegiance, while those with Mu'awiyah have an invalid pledge of allegiance. They are exercising independent legal reasoning, and they have one reward, and He is pleased with them. It is obligatory to refrain from speaking ill of them, to be satisfied with them, and to believe that they are exercising independent legal reasoning: whoever was right has two rewards, and whoever was wrong has one reward.