Narrated Qais: I heard Sa`id bin Zaid bin `Amr bin Nufail saying in the mosque of Al-Kufa. "By Allah, I have seen myself tied and forced by `Umar to leave Islam before `Umar himself embraced Islam. And if the mountain of Uhud could move from its place for the evil which you people have done to `Uthman, then it would have the right to move from its place."
Source: sunnah.com
Other translations
Arabic
حَدَّثَنَا قُتَيْبَةُ بْنُ سَعِيدٍ، حَدَّثَنَا سُفْيَانُ، عَنْ إِسْمَاعِيلَ، عَنْ قَيْسٍ، قَالَ سَمِعْتُ سَعِيدَ بْنَ زَيْدِ بْنِ عَمْرِو بْنِ نُفَيْلٍ، فِي مَسْجِدِ الْكُوفَةِ يَقُولُ وَاللَّهِ لَقَدْ رَأَيْتُنِي وَإِنَّ عُمَرَ لَمُوثِقِي عَلَى الإِسْلاَمِ قَبْلَ أَنْ يُسْلِمَ عُمَرُ، وَلَوْ أَنَّ أُحُدًا ارْفَضَّ لِلَّذِي صَنَعْتُمْ بِعُثْمَانَ لَكَانَ مَحْقُوقًا أَنْ يَرْفَضَّ.
sunnah.com