‘Abdullah ibn ‘Umar radiya Llahu ‘anhu refutes these accusations in an authentic narration as recorded by Imam al Bukhari through the chain of ‘Uthman ibn Mawhib who says:
جاء رجل من أهل مصر حج البيت فرأى قوما جلوسا فقال : من هؤلاء القوم ؟ قال : هؤلاء قريش ، قال : فمن الشيخ فيهم – قالوا عبد الله بن عمر ، قال : يا ابن عمر ! إني سائلك عن شيء فحدثني عنه ، هل تعلم أن عثمان فرّ يوم أحد ؟ قال : نعم ، فقال : هل تعلم أنه تغيب عن بدر ولم يشهد ؟ قال : نعم ، قال : هل تعلم أنه تغيب عن بيعة الرضوان ؟ قال نعم ، قال : الله أكبر ، قال ابن عمر : تعالى أبين لك ، أما فراره يوم أحد فأشهد أن الله عفا عنه وغفر له ، وأما تغيبه عن بدر فإنه كان تحته بنت رسول الله صلى الله عليه وسلم وكانت مريضة ، فقال له رسول الله صلى الله عليه وسلم: إن لك أجر رجل ممن شهد بدرا و سهمه . وأما تغيبه عن بيعة الرضوان فلو كان أحد أعز ببطن مكة من عثمان لبعثه مكانه ، فبعثه رسول الله صلى الله عليه وسلم وكانت بيعة الرضوان بعدما ذهب عثمان إلى مكة ، فقال رسول الله صلى الله عليه وسلم بيده اليمنى : هذه يد عثمان ، فضرب بها على يده ، فقال : لعثمان ، فقال له ابن عمر : اذهب بها الآن معك
An Egyptian who came and performed Hajj saw some people sitting. He enquired, “Who are these people?”
Somebody said, “They are the tribe of Quraysh.”
He said, “Who is the old man sitting amongst them?”
The people replied, “He is ‘Abdullah ibn ‘Umar.”
He said, “O Ibn ‘Umar! I want to ask you about something; inform me regarding it. Do you know that ‘Uthman fled away on the day of Uhud?”
Ibn ‘Umar said, “Yes.”
The man said, “Do you know that ‘Uthman was absent on the day of Badr and did not join it?”
Ibn ‘Umar said, “Yes.”
The man said, “Do you know that he failed to attend the pledge of al Ridwan?”
Ibn ‘Umar said, “Yes.”
The man said, “Allah Akbar!”
Ibn ‘Umar said, “Let me explain to you. As for his flight on the day of Uhud, I testify that Allah has excused him and forgiven him; and as for his absence from the battle of Badr, it was due to the fact that the daughter of Allah’s Messenger salla Llahu ‘alayhi wa sallam was his wife and she was sick then. Rasulullah salla Llahu ‘alayhi wa sallam said to him, ‘You will receive the same reward and share of the booty as anyone of those who participated in the battle of Badr.’ As for his absence from the Bay’ah al Ridwan, had there been any person in Makkah more respectable than ‘Uthman to be sent as a representative, Rasulullah salla Llahu ‘alayhi wa sallam would have sent him instead of him. Rasulullah salla Llahu ‘alayhi wa sallam had sent him, and the incident of Bay’ah al Ridwan happened after ‘Uthman had gone to Makkah. Rasulullah salla Llahu ‘alayhi wa sallam held out his right hand saying, ‘This is the hand of ‘Uthman.’ He held his other hand with it saying, ‘This pledge of allegiance is on the behalf of ‘Uthman.’
Then Ibn ‘Umar said to the man, “Bear these explanations in mind with you.”
To conclude, the aforementioned accusations as mentioned in the Tarikh of Imam al Tabari and other such books of history which have been narrated from ignorant and weak historians, especially the Rawafid, continue to spread a fog around the realities of the lives of the Khalifas and eminent leaders of the ummah. This rings true to a greater degree regarding discussions that surround the era of crisis and fitnah.
It is truly unfortunate that the life story of Amir al Mu’minin, ‘Uthman ibn ‘Affan radiya Llahu ‘anhu has been plagued with such falsities. Narrating incidents in a twisted, biased approach and fabricating events surrounding this enlightened life story has been the drudgery of those seeking to vilify and discredit ‘Uthman radiya Llahu ‘anhu. ‘Uthman radiya Llahu ‘anhu himself had perceived this as understood from the letter he wrote to his governors:
أما بعد ، فإن الرعية قد طعنت في الانتشار ، ونزعت إلى الشر ، وأعداها على ذلك ثلاث : دنيا مؤثرة وأهواء متشرعة ، وضغائن محمولة
The public has split and have taken to evil. This is due to three principle reasons, preference of the world, following of desires, and sentiments of hatred.
Ibn al ‘Arabi commenting on these accusations says:
قالوا متعدین متعلقين برواية كذابين ، جاء عثمان في ولايته بمظالم ومناكير .. هذا كله باطل سندا ومتنا
They say these things as aggressors, citing the narrations of famed liars. They present ‘Uthman as having ushered in oppression and evil during his reign. All of this is fabricated in subject matter and chain of transmissions.
 He is ‘Uthman ibn ‘Abdullah ibn Mawhib al Taymi al Madani, Abu ‘Abdullah. Tabi’i. He narrated from a group of the Sahabah, amongst them Ibn ‘Umar, Abu Hurairah, and Umm Salamah.
He passed away the year 160 A.H/679 A.D. His life has been recorded by Khalifah: Al Tabaqat, pg. 273; Al ‘Ijli: Tarikh al Thiqat, pg. 328; Ibn Abi Hatim: Al Jarh wa al Ta’dil, vol. 6 pg. 155; Al Dhahabi: Al Kashif, vol. 2 pg. 221; and Ibn Hajar: Al Tahdhib, vol. 7 pg. 132.
 Sahih al Bukhari, vol. 4 pg. 203.
 Ibn ‘Asakir: Tarikh Dimashq, pg. 240.
 Ibn al ‘Arabi: Al ‘Awasim, pgs. 61-63.