The spirit of man is the candle of the Lord , searching all the inward parts of the belly. -Proverbs 20:27, KJV
In Matthew 5, Jesus said we Christians are the light of the world who should let that light shine by doing good works that bring others to the Lord.
Now, many people attempt to do good works without bothering to include God, both Christians and non-Christians.
Isaiah was the one who reminded us that our works done apart from God are … *ahem* … dirty rags. (64:6. Ask your pastor if you do not know the full meaning of “dirty rags”.)
What does all of this have to do with Proverbs 20:27?
The light within us is God, the one who sustains our lives, even when we are living apart from His ways. In both Jeremiah (31:33) and Hebrews we are told that in these last days God has written His Law on our minds and hearts.
One way of looking at this is that He has seared our conscience with what is right. We “instinctively know” what is right and wrong.
Yet, when we do not live in accordance with His Spirit, even our best intentions are tainted by our selfish, sinful desires and actions.
It is when you get that feeling in the pit of your stomach that something is not right. So, when God searches our “inward parts of the belly” (i.e. our hearts), He can see our selfish, sinful leanings.
But He also regenerates our hearts and minds by His Spirit to do truly good, God-honoring and glorifying works.