The Messenger of Allah ﷺ said, "The martyr feels nothing of the pain of being killed except as one of you feels the pinch of an insect bite."
حدثنا صفوان أخبرنا ابن عجلان عن القعقاع بن حكيم عن أبي صالح
أن رسول الله ﷺ قال ما يجد الشهيد من مس القتل إلا كما يجد أحدكم مس القرصة
Its chain of transmission is sahih. Tirmidhi related it, 3:19, from Muhammad bin Bashshar and Ahmad bin Nasr Nisaburi and several others, who said, "Safwan bin Isa related to us," then he mentioned it with this chain. He said, "This is a hasan gharib sahih hadith." Ibn Majah likewise related it, 2802, from Muhammad bin Bashshar, Ahmad bin Ibrahim Dawraqi, and Bishr bin Adam, who said, "Safwan bin Isa related to us."Nasai related it in similar wording, 2:62, from Imran bin Yazid, from Hatim bin Ismail, from Muhammad bin Ajlan. Munziri mentioned it in Targhib wal-Tarhib, 2:192, and attributed it to Tirmidhi, Nasai, Ibn Majah, and Ibn Hibban in his Sahih. Suyuti attributed it in Ziyadat al-Jami al-Sagheer to Ibn Hibban as well. See Fath al-Kabir, 3:126.