Matthew 24:50
the lord of that servant will come in a day when he doesn't expect it, and in an hour when he doesn't know it,
Matthew 24:42-44
Watch therefore, for you don't know in what hour your Lord comes.
1 Thessalonians 5:2-3
For you yourselves know well that the day of the Lord comes like a thief in the night.
Revelation 3:3
Remember therefore how you have received and heard. Keep it, and repent. If therefore you won't watch, I will come as a thief, and you won't know what hour I will come upon you.
Proverbs 29:1
He who is often rebuked and stiffens his neck will be destroyed suddenly, with no remedy.