From "The Biography of Uthman Ibn Affan, Dhun Noorayn" Page 434 by Ali Muhammad AsSallabi
[Someone asked Umar Ibn Abdul Aziz about the fitnah] "and he responded by qouting the words of Allah,
Tilka ummatun qad khalet laha ma kasabat wa lakum ma kasabtum, wala tusaloona amma kaanoo ya'lamoon.
'That was a nation who has passed away. They shall receive the reward of what they earned and you of what you earn. And you will not be asked of what they used to do.' (Al-Baqarah 2:134)
There is a reason for this prohibition, which is the fear that it may lead to criticism and impugning their honour, which in turn could lead to the wrath and anger of Allah. But if this reason no longer applies, then it seems that there is no problem with it, so long as discussing the details of what happened will not lead to criticizing them at all. In that case, there is nothing wrong with studying this matter in depth, examining its causes, motives, precise details, results and consequences for the society of the Sahaba and for those who came after them. Some of the scholars, such as Ibn Katheer, al-Tabari and other, wrote about the events of that critical period of Islamic history, and discussed in detail many of the issues that had to do with the fitnah..."
It is reported that Shaikh Al Islam Ibn Taymiyyah said "And the aqeedah of Ahl ul-Sunnah Wal Jama'ah is to cease talking about the disputes of the Sahabah because all the athar (sayings) reported about their defections are either lies, fabrications, (or have been) added to, (or information which has been) deleted from and out of context. What remains of the Saheeh have excuses regarding them, either they (the Sahabah) are Mujtahid who get two rewards or one reward (if they have the Wrong Ijtihad). " (From the book Ahl ul Sunnah wal Jammah.)
[Someone asked Umar Ibn Abdul Aziz about the fitnah] "and he responded by qouting the words of Allah,
Tilka ummatun qad khalet laha ma kasabat wa lakum ma kasabtum, wala tusaloona amma kaanoo ya'lamoon.
'That was a nation who has passed away. They shall receive the reward of what they earned and you of what you earn. And you will not be asked of what they used to do.' (Al-Baqarah 2:134)
There is a reason for this prohibition, which is the fear that it may lead to criticism and impugning their honour, which in turn could lead to the wrath and anger of Allah. But if this reason no longer applies, then it seems that there is no problem with it, so long as discussing the details of what happened will not lead to criticizing them at all. In that case, there is nothing wrong with studying this matter in depth, examining its causes, motives, precise details, results and consequences for the society of the Sahaba and for those who came after them. Some of the scholars, such as Ibn Katheer, al-Tabari and other, wrote about the events of that critical period of Islamic history, and discussed in detail many of the issues that had to do with the fitnah..."
It is reported that Shaikh Al Islam Ibn Taymiyyah said "And the aqeedah of Ahl ul-Sunnah Wal Jama'ah is to cease talking about the disputes of the Sahabah because all the athar (sayings) reported about their defections are either lies, fabrications, (or have been) added to, (or information which has been) deleted from and out of context. What remains of the Saheeh have excuses regarding them, either they (the Sahabah) are Mujtahid who get two rewards or one reward (if they have the Wrong Ijtihad). " (From the book Ahl ul Sunnah wal Jammah.)