And He it is Who takes you back at night (by taking away your consciousness during your sleep) and He knows how you keep yourselves busy during the day, then He raises you up therein (day, by returning your consciousness) that you may fulfill the appointed term, then towards Him is your return, then He will inform you of that which you used to do. (R 7)
Allah (SWT) causes human beings to sleep during night and He keeps them awake during the day. This process continues till death when they are returned to Him Who will inform them of their deeds.