Every way of a man is right in his own eyes,
but the Lord weighs the heart.
Note two insights in this proverb in relation to a Christian. First, a Christian will defend his behavior either through using scripture for justification or by appealing to conscience. There is the husband who defended being critical of his wife by appealing to Ephesians 5:25-27, which refers to Christ has sanctifying the church. Likewise, Christians have defended rude behavior as being bold for Christ and zealous for truth. In every case, the person believes he is doing what is right. In his own eyes, he is being faithful to God.
Second, the Lord weighs the heart. He weighs the heart, not the action. He weighs the true motive of the Christian, not what the Christian thinks is his motive. The mistake of the Christian is to believe that he looks within his own heart with clear sight. That is precisely what we are weakest at doing. We cannot weigh our own heart. Only God can do so.
What is the practical input of this reality - that we see a favorably distorted view of ourselves and only the Lord weighs with accuracy the heart? It should make us humble. It should make us slow to make judgment of others, especially to make unfavorable judgments of others in relation to ourselves. We should be zealous to study God's Word so that it shines a light on our hearts. We should never be quick to defend our hearts, knowing that we may very well be wrong. Even when we may be accurate about what we do see in ourselves, we never do know the full picture. Again, only the Lord weighs truly the heart.
Finally, it should lead us to rely wholly on the mercy of God. If God were to measure out justice according to what he weighs in our hearts, we would all perish. God weighs and then he measures out to us according to his mercy. Have you thanked him today for such mercy?