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)." (PT)
English reference (PT): Vol. 4, Book 24, Hadith 2802 (PT)
Arabic reference (PT): Book 24, Hadith 2908 (PT)