Thomas Aquinas

And he adds the punishment, where it says, therefore shall this iniquity be to you, signifying sudden punishment by the likeness of ruin, which lies hidden for a long time in a wall that falls suddenly in the end: for the destruction thereof shall come on a sudden: for when they shall say: peace and security; then shall sudden destruction come upon them (1 Thess 5:3).

Commentary on Isaiah ↗