Matthew 24:50
the master of that slave will come on a day that he does not expect and at an hour that he does not know,
Matthew 24:42-44
Therefore be on the alert, because you do not know what day your Lord is coming!
1 Thessalonians 5:2-3
for [you] yourselves well know that the day of the Lord is coming in the [same] way as a thief in the night.
Revelation 3:3
Therefore remember how you have received and heard, and observe [it], and repent. If therefore you are not on the alert, I will come like a thief, and you will never know [at] what hour I will come against you.
Proverbs 29:1
A man who is reproved, being stubborn of neck-- suddenly he will be broken, and there will not be healing.