Hadith Qudsi 32
32) Narrated Anas: Allah's Messenger said: A man from among people of Paradise will be brought forward. Allah will ask him: 0 Son of Adam! How did you find your home? He will reply: 0 my Lord! It is the best home, then Allah will say: Ask and wish anything you like. The man will say: I would ask You to send me back to the world in order to be killed in Your way ten times. (This is because of the superiority of the martyrdom and the high position which martyrs would be made to occupy in heaven).
(This Hadith is sound and reported by Nasa'i).