This verse follows up on the insult of Zephaniah 1:12 that in their hearts the Judahites had been levelling against the Lord, that the Lord will not do good, nor will he do evil.
The irony then is that the very God who they thought did nothing, whether good or bad, was at that moment preparing an aggressor who would search Jerusalem to punish those people and remove the wealth in which they trusted.
1 Their God is no absentee God. And they will not be able to do a thing to stop his judgment.
13 Their goods shall be plundered, and their houses laid waste. Though they build houses, they shall not inhabit them; though they plant vineyards, they shall not drink wine from them.”