Albert Barnes Commentary 1 John 3:20

"because if our heart condemn us, God is greater than our heart, and knoweth all things." — 1 John 3:20 (ASV)

For if our heart condemn us. We cannot hope for peace from any expectation that our own hearts will never accuse us, or that we ourselves can approve of all that we have done. The reference here is not so much to our past lives as to our present conduct and behavior.

The object is to encourage Christians to live in such a way that their hearts will not condemn them for any secret sins, while their outward behavior may be unblemished. The general sentiment is that if they live in such a way that their own hearts would condemn them for present insincerity and hypocrisy, they could have no hope of peace, for God knows all that is in the heart.

In view of the past—when the heart accuses us of what we have done—we may find peace through such evidences of piety as will alleviate the troubles of an agitated soul (1 John 3:9), but we cannot have such peace if our hearts condemn us for indulging in secret sins now that we profess to be Christians.

If our hearts condemn us for present insincerity and for secret sins, we can never persuade or soothe them by any external act of piety. In view of the consciousness of past guilt, we may find peace; we can find none if there is a present purpose to indulge in sin.

God is greater than our heart, and knoweth all things. We cannot hope to find peace by hiding anything from his view, or by any supposition that he is not acquainted with the sins for which our consciences trouble us. He knows all the sins of which we are conscious and sees all their guilt and aggravation as clearly as we do.

He knows more than this. He knows all the sins we have forgotten; all those acts which we try to persuade ourselves are not sinful, but which are evil in his sight; and all those aggravations accompanying our sins which it is impossible for us to fully and distinctly conceive. He is more disposed to condemn sin than we are; he looks on it with less allowance than we do.

We cannot hope, then, for a calm mind based on any supposition that God does not see our sins as clearly as we do, or in any hope that he will look on them with more favor and indulgence.

Peace cannot be found in indulging in sin with the hope that God will not perceive or regard it, for we can sooner deceive ourselves than we can him.

And while, therefore, (1 John 3:19), in reference to the past, we can only persuade our hearts or soothe their agitated feelings with evidence that we are of the truth now and that our sins are forgiven; in reference to the present and the future, the heart can be kept calm only by such a course of life that our own hearts and our God will approve the manner in which we live.