Matthew 24:50
the master of that servant will come on a day when he does not expect him and at an hour he does not know
Matthew 24:42-44
Therefore, stay awake, for you do not know on what day your Lord is coming.
1 Thessalonians 5:2-3
For you yourselves are fully aware that the day of the Lord will come like a thief in the night.
Revelation 3:3
Remember, then, what you received and heard. Keep it, and repent. If you will not wake up, I will come like a thief, and you will not know at what hour I will come against you.
Proverbs 29:1
He who is often reproved, yet stiffens his neck, will suddenly be broken beyond healing.