Matthew 24:50

that slave's master will come back some day when he does not expect him, and at some time of which he does not know

Matthew 24:42-44

So you must be on the watch, for you do not know on what day your Master is coming.

1 Thessalonians 5:2-3

for you yourselves know perfectly well that the Day of the Lord is to come like a thief in the night.

Revelation 3:3

So remember what you received and heard, and obey it, and repent. If you do not wake up, I will come like a thief, and you will not know at what hour I am coming upon you.

Treasury of Scripture Knowledge

Summary

The lord of that servant shall come in a day when he looketh not for him, and in an hour that he is not aware of,

Bible References

Come

Matthew 24:42
So you must be on the watch, for you do not know on what day your Master is coming.
1 Thessalonians 5:2
for you yourselves know perfectly well that the Day of the Lord is to come like a thief in the night.
Revelation 3:3
So remember what you received and heard, and obey it, and repent. If you do not wake up, I will come like a thief, and you will not know at what hour I am coming upon you.