"O Messenger of Allah, why will the believers be tested in their graves except the martyr?" He said: "The flashing of the swords above his head is trial enough." (Using translation from Nasāʾī 2053)  

عَنْ رَجُلٍ مِنْ أَصْحَابِ النَّبِيِّ ﷺ أَنَّ رَجُلًا قَالَ يَا رَسُولَ اللهِ مَا بَالُ الْمُؤْمِنِينَ يُفْتَنُونَ فِي قُبُورِهِمْ إِلَّا الشَّهِيدَ؟ قَالَ «كَفَى بِبَارِقَةِ السُّيُوفِ عَلَى رَأْسِهِ فِتْنَةً»  

[Machine] Narrated Abu Uthman repeatedly and raised it once to the Prophet ﷺ .  

حَدَّثَنَا أَبُو عُثْمَانَ مِرَارًا وَرَفَعَهُ مَرَّةً إِلَى النَّبِيِّ ﷺ