It wasnarrated from Abu Hurairah that the Messenger of Allah (ﷺ)said:
"The martyr does not feel anything more when he is killed thanoneof you feels if he is pinched (by a bug)." (RU)
English reference (RU): Vol. 4, Book 24, Hadith 2802 (RU)
Arabic reference (RU): Book 24, Hadith 2908 (RU)