The Prophet ﷺ said, "Whoever asks Allah sincerely from his heart to be killed in His path, Allah will grant him the reward of a martyr."
حدثنا أحمد بن منيع حدثنا روح بن عبادة حدثنا ابن جريج عن سليمان بن موسى عن مالك بن يخامر السكسكي
عن النبي ﷺ قال من سأل الله القتل في سبيله صادقا من قلبه أعطاه الله أجر الشهيد
No references are available.
[Its isnad is sahih] Nasai also reported it, 6/25, 26, hadith 3143 (Jihad, chapter on the reward of one who fights in the cause of Allah for the duration of a she-camel's milking), from the hadith of Ibn Jurayj, in a longer form, and he made clear that he had heard it directly.