Musnad Ahmad 30:2377

Abu Mu'awiyah and Ya'la ibn 'Ubayd narrated to us, they said: Al-A'mash narrated to us, from Abu Salih, from Abu Hurayrah, who said: The Messenger of Allah (peace and blessings of Allah be upon him) said: "Indeed, for every prophet there is a supplication that is answered, so every prophet hastened his supplication. And I have stored my supplication—meaning intercession—for my nation. So it shall reach, if Allah wills, whoever dies not associating anything with Allah." Ya'la said: Intercession.