Sunan Ibn Majah
2802
Hasan Sahih+3

It was narrated from Abu Hurairah that the Messenger of Allah (ﷺ) said:“The martyr does not feel anything more when he is killed than one of you feels if he is pinched (by a bug).”

Hasan SahihAl-Albani
Hasan SahihMuhammad Fouad Abd al-Baqi