سنن النسائي

It was narrated that Abu Hurairah said: "I heard the Messenger of Allah (ﷺ) say: 'By the One in Whose hand is my soul, were it not that some men among the believers would not like to stay behind when I went out (to fight), and I could not find any mounts for them, I would not have stayed behind from any campaign that fought in the cause of Allah. By the One in Whose hand is my soul, I wish that I could be killed in the cause of Allah, then brought back to life, then killed, then be brought back to life, then killed.'"