Passage
When they may say, Peace and safety, then sudden destruction comes upon them, as travail upon her that is with child; and they shall in no wise escape.
1 Thessalonians 5:3 (DBY)
Nearby Context
1 Thessalonians 5:1 But concerning the times and the seasons, brethren, ye have no need that ye should be written to,
1 Thessalonians 5:2 for ye know perfectly well yourselves, that the day of [the] Lord so comes as a thief by night.
1 Thessalonians 5:3 When they may say, Peace and safety, then sudden destruction comes upon them, as travail upon her that is with child; and they shall in no wise escape.
1 Thessalonians 5:4 But *ye*, brethren, are not in darkness, that the day should overtake you as a thief:
1 Thessalonians 5:5 for all *ye* are sons of light and sons of day; we are not of night nor of darkness.
Study Lenses
The verse centers on "peace", "safety", "sudden", "destruction", "comes", "upon", and "travail". It is saying that the verse draws attention to "peace" and "safety", so its meaning should be read from those terms before moving to application.
The nearby context moves from verse 2's "for ye know perfectly well yourselves that..." into verse 4's "But ye brethren are not in darkness...", so "peace" and "safety" belong inside that flow. In 1 Thessalonians context, the local focus is Christ, faith, and discipleship.
A plain takeaway is to answer the verse's own emphasis on "peace" and "safety" with trust shaped by these words, not by a vague optimism outside the passage.