'Thief' in the Bible

Remember therefore how thou hast received and heard, and keep it and repent. If therefore thou shalt not watch, I will come upon thee as a thief, and thou shalt not know at what hour I shall come upon thee.

(Behold, I come as a thief. Blessed is he that watches and keeps his garments, that he may not walk naked, and that they may not see his shame.)