And it shall come to pass at that time, that I will search Jerusalem with candles, and punish the men that are settled on their lees: that say in their heart, The LORD will not do good, neither will he do evil.
At that time ... I will search Jerusalem with candles - or lamps; so as to leave no dark corner in it wherein sin can escape the punishment, of which the Chaldeans are my instruments (cf. Zephaniah 1:13). As God searcheth out the sin of the wicked for punishment, so His Spirit searcheth out His own elect, to take them out of the darkness of this world for salvation, like the woman (Luke 15:8) who, having lost one piece of silver, literally a candle, and swept the house, and sought diligently until she found it. Compare Psalms 44:21, "Shall not God search this out? for he knoweth the secrets of the heart;" and Amos 9:3, "Though they hide themselves in the top of Carmel, I will search and take them out thence."
And punish the men that are settled on their lees - hardened or crusted. Image from the crust formed at the bottom of wines long left undisturbed (Jeremiah 48:11). The effect of wealthy undisturbed ease ("lees") on the ungodly is hardening; they become stupidly secure (cf. Psalms 55:19; Amos 6:1).
That say in their heart, The Lord will not do good, neither will he do evil. They deny that God regards human affairs, or renders good to the good, or evil to the evil, but that all things go hap-hazard (Psalms 10:4, "God is not in all his (the wicked man's) thoughts ... thy judgments are far above out of his sight;" Malachi 2:17).