James speaking to believers calls them sinners when they are sinning.
James 4:1-10
What is the source of quarrels and conflicts among you? Is not the source your pleasures that wage war in your members? You lust and do not have; so you commit murder. You are envious and cannot obtain; so you fight and quarrel. You do not have because you do not ask.
You ask and do not receive, because you ask with wrong motives, so that you may spend it on your pleasures. You adulteresses, do you not know that friendship with the world is hostility toward God?
Therefore whoever wishes to be a friend of the world makes himself an enemy of God. Or do you think that the Scripture speaks to no purpose: “He jealously desires the Spirit which He has made to dwell in us”?
But He gives a greater grace. Therefore it says, “God is opposed to the proud, but gives grace to the humble.” Submit therefore to God. Resist the devil and he will flee from you. Draw near to God and He will draw near to you. Cleanse your hands, you sinners; and purify your hearts, you double-minded.
Be miserable and mourn and weep; let your laughter be turned into mourning and your joy to gloom. Humble yourselves in the presence of the Lord, and He will exalt you.