Musnad Ahmad 30:3156

'Abd al-Rahman narrated to us, from Zuhayr, from al-'Ala', from his father, from Abu Hurayrah, from the Prophet, peace and blessings of Allah be upon him, who said: "Indeed, a man may perform the deeds of the people of Paradise for a long time, then Allah seals his deeds with the deeds of the people of the Fire, so He makes him one of the people of the Fire. And indeed, a man may perform the deeds of the people of the Fire for a long time, then Allah seals his deeds with the deeds of the people of Paradise, so He makes him one of the people of Paradise, and He admits him into Paradise."