Musnad Ahmad 30:3641

'Abd al-Malik ibn 'Amr narrated to us, Zuhayr narrated to us, from al-'Ala', from his father, from Abu Hurayrah, from the Prophet (peace and blessings of Allah be upon him), who said: "Hasten to perform deeds before tribulations come like pieces of a dark night; a man will wake up as a believer and go to sleep as a disbeliever, and he will go to sleep as a believer and wake up as a disbeliever, selling his religion for a small amount of worldly goods."