The heart is the real test of a man’s character. It is not what he says or what he does by which the man may be always known. He may say and do things that are right, from false and unworthy motives, while his heart is altogether wrong. The heart is the man. “As he thinks in his heart, so he is” (Proverbs 23:7).
The heart is the right test of a man’s religion. It is not enough that a man holds to correct doctrine, and maintains a proper outward form of godliness. What is in his heart? That is the great question. That is what God looks at. “Man looks at the outward appearance, but the Lord looks at the heart” (1 Samuel 16:7). This is what Paul lays down distinctly as the standard measure of the soul: “A man is a Jew if he is one inwardly; and circumcision is circumcision of the heart” (Romans 2:28). Who can doubt that this mighty sentence was written for Christians as well as for Jews? He is a Christian, the apostle would have us know, which is one inwardly, and baptism is that of the heart.
J. C. Ryle