Hadith

 وَ بِهَذَا اَلْإِسْنَادِ عَنْ أَحْمَدَ بْنِ أَبِي عَبْدِ اَللَّهِ عَنْ حُصَيْنِ بْنِ عُمَرَ قَالَ قَالَ أَبُو عَبْدِ اَللَّهِ ع إِنَّ اَلْمُؤْمِنَ أَشَدُّ مِنْ زُبَرِ اَلْحَدِيدِ إِنَّ اَلْحَدِيدَ إِذَا أُدْخِلَ اَلنَّارَ تَغَيَّرَ وَ إِنَّ اَلْمُؤْمِنَ لَوْ قُتِلَ ثُمَّ نُشِرَ ثُمَّ قُتِلَ لَمْ يَتَغَيَّرْ قَلْبُهُ.

 (The same previous series of relaters)… from Hussein bin Amr said that Abu Abdullah (a) said: The believer is firmer than blocks of iron. Iron is changed when it is subjected to fire, while the believer will not be changed even if he is killed, cut by a saw, and then killed anew.

Ṣifāt al-Shīʿa

Book 1, Chapter 47