Sahih al-Bukhari 6942
Sahih al-Bukhari · Book 89: (Statements made under) Coercion · Whoever preferred to be beaten killed and humiliated rather than to revert to Kufr
Narrated Qais:
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.
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." (See Hadith No. 202, Vol. 5)