Adam Clarke on Revelation 16:15

Behold, I come as a thief - Here is a sudden but timely warning to put every man on his guard, when this sudden and generally unexpected tribulation should take place.

Keepeth his garments, lest he walk naked - Here is a plain allusion to the office of him who was called the prefect or overseer, of the mountain of the temple. His custom was to go his rounds during the watches of the night; and if he found any of the Levites sleeping on his watch, he had authority to beat him with a stick, and burn his vestments. See Middoth, fol. 34, 1, and Tamid. fol. 27, 2; 28, 1. Such a person being found on his return home naked, it was at once known that he had been found asleep at his post, had been beaten, and his clothes burnt; thus his shame was seen - he was reproached for his infidelity and irreligion.