This may help us realize how God is in charge of our circumstances. He should pray. Let him sing songs of praise. He should call the elders of the church to pray over him and anoint him with oil in the name of the Lord. If he has sinned, he will be forgiven.
Confession of sins produces patience.
The prayer of a righteous man is powerful and effective. Nothing promotes patience among Christians more than forgiveness. I can only surmise that this warring factious church to which James writes needed to clear the air. The only way they could clear the air was through confession and forgiveness. Patience produces powerful and effective prayers.