Musnad Abu Ya'la al-Mawsili 3:92

Ubayd Allah narrated to us, Abd al-Rahman ibn Mahdi narrated to us, Za'idah narrated to us, from Mansur ibn al-Mu'tamir, from Rib'i ibn Hirash, from Ali, that the Prophet (peace and blessings of Allah be upon him) said: "A servant does not believe until he believes in four: in the resurrection after death, and he believes in the decree."