50 on a day when he is not expecting him, and at an hour which he does not know, the Master of that servant will arrive
Matthew 24:50 Cross References - MNT
Matthew 24:42-44
42 Keep guard then, for you do not know the day on which your Master is coming.
43 But know this, that if the master of the house had known in what watch the thief was coming, he would have been on his guard, and would not have allowed his house to be broken into.
44 Therefore you also must be ready, for in an hour when you do not expect him, the Son of man is coming.
1 Thessalonians 5:2-3
Revelation 3:3
3 Call to mind, then, what you have received and heard, and hold to it, and repent. Unless you are on the watch, I will come as a thief, and you will never know at what hour I am coming upon you.