'Thief' in the Bible

So remember and take to heart the lessons you have received and heard. Keep and obey them, and repent [change your sinful way of thinking, and demonstrate your repentance with new behavior that proves a conscious decision to turn away from sin]. So then, if you do not wake up, I will come like a thief, and you will not know at what hour I will come to you.

(“Behold, I am coming like a thief. Blessed is he who stays awake and who keeps his clothes [that is, stays spiritually ready for the Lord’s return], so that he will not be naked—spiritually unprepared—and men will not see his shame.”)