Sahih Muslim 1908
Sahih Muslim · Book 33: The Book on Government · It is recommended to seek Martyrdom in the Cause of Allah, Exalted is He.
It has been narrated on the authority of Anas b. Malik that the Messenger of Allah (may peace he upon him) said:
حَدَّثَنَا شَيْبَانُ بْنُ فَرُّوخَ ، حَدَّثَنَا حَمَّادُ بْنُ سَلَمَةَ ، حَدَّثَنَا ثَابِتٌ ، عَنْ أَنَسِ بْنِ مَالِكٍ ، قَالَ قَالَ رَسُولُ اللَّهِ صلى الله عليه وسلم " مَنْ طَلَبَ الشَّهَادَةَ صَادِقًا أُعْطِيَهَا وَلَوْ لَمْ تُصِبْهُ " .
Who seeks martyrdom with sincerity shall get its reward, though he may not achieve it.