Musnad Ahmad 32:2139

Bahz narrated to us, Hammam narrated to us, he said: Qatadah informed us, from Anas, that the Prophet, peace and blessings of Allah be upon him, said: "There is no one among the people of Paradise who would be pleased to return to the world, even if he were to have ten times its equivalent, except for the martyr. For he wishes to return to the world and be martyred ten times, because of what he sees of the merit."