Sahih Bukhari Volume 9, Book 89, Hadith 6944

حَدَّثَنَا سَعِيدُ بْنُ سُلَيْمَانَ، حَدَّثَنَا عَبَّادٌ، عَنْ إِسْمَاعِيلَ، سَمِعْتُ قَيْسًا، سَمِعْتُ سَعِيدَ بْنَ زَيْدٍ، يَقُولُ لَقَدْ رَأَيْتُنِي وَإِنَّ عُمَرَ مُوثِقِي عَلَى الإِسْلاَمِ، وَلَوِ انْقَضَّ أُحُدٌ مِمَّا فَعَلْتُمْ بِعُثْمَانَ كَانَ مَحْقُوقًا أَنْ يَنْقَضَّ‏.

Narrated By Qais : I heard Sa'id bin Zaid saying, "I have seen myself tied and forced by 'Umar to leave Islam (Before 'Umar himself embraced Islam). And if the mountain of Uhud were to collapse for the evil which you people had done to 'Uthman, then Uhud would have the right to do so."