Musnad Ahmad 30:460

Abu Kamil narrated to us, Ibrahim and Ya'qub narrated to us, my father narrated to us, Ibn Shihab narrated to us, from Ubayd Allah ibn Abd Allah, from Abu Hurayrah, who said: The Messenger of Allah (peace and blessings of Allah be upon him) said: "None of you should wish for death. Either he is a doer of good, so perhaps he may increase in goodness; or he is a doer of evil, so perhaps he may seek to please [Allah]."