Matthew 24:50
the master of that servant will arrive on a day when he is not expecting him and at an hour of which he has not been informed;
Matthew 24:42-44
Be on the alert therefore, for you do not know the day on which your Lord is coming.
1 Thessalonians 5:2-3
For you yourselves know perfectly well that the day of the Lord comes like a thief in the night.
Revelation 3:3
Be mindful, therefore, of the lessons you have received and heard. Continually lay them to heart, and repent. If, however, you fail to rouse yourself and keep awake, I shall come upon you suddenly like a thief, and you will certainly not know the hour at which I shall come to judge you.