Lets try again: To what event does the phrase thief in the night refer?
(Im not supposed to read your mind.)
Lets first look at where the term thief in the night came from.
In Revelation 16:15 we see the most definitive example of the "thief" analogy being applied to the return of Christ: Behold, I come as a thief. Blessed is he that watcheth, and keepeth his garments, lest he walk naked, and they see his shame.
During the time that the Jewish Temple was standing when Jesus was here the first time, the high priest and the captain of the guard were known as the thief in the night and, this is why. There were watch posts at the Temple where the priest had to be watching. One of the things they had to watch for was that the fire on the altar would not go out. This was a Godly fire that fell on the altar and it was commanded by God that this fire never go out. The priest had to watch this fire. If her priest was found to be sleeping when the captain of the guard checked on his rounds, the captain of the guard would take his torch, which was next to the altar fire, and set the priests garment on fire with the torch. The priest would be awaken by the fire, he would get up run through the Temple tearing off the garments that were on fire, and the shame of the priests nakedness would appear.
Look what it says in Isaiah chapter 26:20-21 Come, my people, enter thou into thy chambers, and shut thy doors about thee: hide thyself as it were for a little moment, until the indignation be overpast. For, behold, the LORD cometh out of his place to punish the inhabitants of the earth for their iniquity: the earth also shall disclose her blood, and shall no more cover her slain.
These are the chambers Jesus will keep his church in while the seven-year tribulation is taking place on earth.
The church, bride of Christ, will be hidden from these terrible times that will befall the earth during the tribulation.
The phrase phrase is used in relation to the catching away or Rapture of the believers. Those of us who understand know what to watch for. We know the season.