Zephaniah 1:7-11 describes the judgments that were going to come on the city of Jerusalem. Vs. 12 tells reason for its judgment.
Zeph. 1:12 “And it will come about at that time That I will search Jerusalem with lamps, And I will punish the men Who are stagnant in spirit [that are settled on their lees - KJV], Who say in their hearts, 'The LORD will not do good or evil!'”
They were in such a poor spiritual condition because they were “men that are settled on their lees” (in the King James and American Standard Versions). The New Revised Standard Version updates the figure, giving it as “people who rest complacently on their dregs.”
Pictured here is undisturbed wine. The dregs (lees) have precipitated out, and have not been disturbed for a very long time. When bottles of wine are not rotated in their racks or casks of wine that are not turned, the wine becomes thick and it’s flavor is unchanged. For a cask of wine to sit for so long undisturbed implies prosperity and affluence. As a result, good wine becomes great and bad wine becomes worse.
Some of the newer translations simply give the meaning of Zephaniah’s figure of speech. The New American Standard speaks of the people being “stagnant in spirit” and the New King James says that they “are settled in complacency.” Speaking either literally or figuratively, it is obvious that the conscience of these people has not been exercised for a long time. They are wicked men long set in evil who forgot that God will examine everything.