Matthew 24:50
the Lord of that servant shall come in a day when he does not look for Him, and in an hour which he does not know.
Matthew 24:42-44
Therefore watch; for you do not know what hour your Lord comes.
1 Thessalonians 5:2-3
For you yourselves know accurately that the day of the Lord comes like a thief in the night.
Revelation 3:3
Remember then how you have received and heard, and hold fast, and repent. Therefore if you will not watch, I will come upon you as a thief, and you will not know what hour I will come upon you.
Proverbs 29:1
A man who hardens his neck when reproved shall be suddenly broken, and there will be no healing.