Search me, O God, and know my heart;

test me and know my anxious thoughts.

See if there is any offensive way in me,

and lead me in the way everlasting (Ps 139:23-24).

In this scripture, the psalmist is asking God to check his heart if there are any wrong ideas, thoughts or attitudes in him. This is a wonderful prayer that all of us should have. But think. Hearing this prayer, how does God actually point out to us such wrong ideas and attitudes—the offensive way in us? In other words, how do we find out that particular attitudes we have in us are wrong? Having lived with those ideas for many years, we are usually blind to them, and never ask ourselves if there is any offensive way in us. So, how does God let us see it so that we can change? For that, we have the following scripture in the New Testament:

For the word of God is living and active. Sharper than any double-edged sword, it penetrates even to dividing soul and spirit, joints and marrow; it judges the thoughts and attitudes of the heart (Heb 4:12).

It is by the word of God that he shows us the offensive way we may have in us—the thoughts and attitudes that are not God’s will. Like a teacher who teaches and admonishes us with love and patience, the word of God “judges the thoughts and attitudes of the heart.” God’s word is like an x-ray which penetrates your body, and sees what is happening underneath the skin. It goes beyond the external things of us—words that our physical ears hear, or deeds that our physical eyes see. It reveals the hidden motivations and thoughts we have in our hearts. So, the writer of Hebrews says:

Nothing in all creation is hidden from God's sight. Everything is uncovered and laid bare before the eyes of him to whom we must give account (v. 13).

Note that he talks about “the eyes of him.” Keep in mind that for ancient people, eyes are something that shines. In fact, through those eyes, God sees what is in our hearts—every detail of our thoughts and emotions. And it is through the same eyes that God’s word gives light to our heart. Jesus said:

Do you bring in a lamp to put it under a bowl or a bed? Instead, don't you put it on its stand? For whatever is hidden is meant to be disclosed, and whatever is concealed is meant to be brought out into the open. If anyone has ears to hear, let him hear (Mark 4:21-23).

Here, ears to hear and eyes to see are used metaphorically in the same meaning. If you have ears to hear, you also have eyes to see. When your eyes give light to your heart, hidden things are disclosed, and you can see that they are there, and what they are. And if they are wrong and not God’s will, you come to see it so that you can change. That is how God’s word works for you. But the important thing is that you should not reject that light by “putting it under a bowl or a bed.” Since we all have a free will, we can reject it if we want to. The following story of the Pharisees and the teachers of the law in Mark is one example of that.

The Pharisees and some of the teachers of the law who had come from Jerusalem gathered around Jesus and saw some of his disciples eating food with hands that were "unclean," that is, unwashed. … So the Pharisees and teachers of the law asked Jesus, "Why don't your disciples live according to the tradition of the elders instead of eating their food with ‘unclean’ hands (7:1-5)?"

And to them, Jesus spoke the following words giving light to their hearts, but note how they reacted:

Isaiah was right when he prophesied about you hypocrites; as it is written: "These people honor me with their lips, but their hearts are far from me. They worship me in vain; their teachings are but rules taught by men (vv. 6-7).”