Mark 13:34-37 (KJV)
34 For the Son of Man is as a man taking a far journey, who left his house, and gave authority to his servants, and to every man his work, and commanded the porter to watch.
35 Watch ye therefore: for ye know not when the master of the house cometh, at even, or at midnight, or at the cockcrowing, or in the morning:
36 Lest coming suddenly he find you sleeping.
37 And what I say unto you I say unto all, Watch.