The mammon of unrighteousness (verse 9), or here ‘unrighteous mammon’, is Christ’s name for the riches which exist on earth. It need not be unrighteous, but that is how it is used by members of a fallen human race.
Why is covetousness such a great evil? Because it replaces the Lord with the token gifts with which he blesses us. It wants to take these things and refuse to acknowledge where they came from, and to refuse to give thanks. From heaven’s perspective it is madness, because it cuts us off from the true and infinite source of all our good, from the Lord himself. Nothing that the Lord gives can become a substitute for him. Our true joy in receiving what he puts in our hands, is to know that all is a gift which comes from his love for us.
Covetousness is a fatal flaw which affects us so deeply. Once it finds its way into a human heart, it affects all our interactions with the world around us. If somehow – and this is impossible – the man who is unfaithful with regard to riches were to find his way into heaven, he would still be unfaithful; he would still be covetous. He would take his character with him into heaven. The cure must begin in this life, or it will never begin at all. Heaven has seen enough of how we have behaved on earth, in order to know that we are not fit for heaven if we have been unfaithful in earthly riches. ‘Who will commit to your trust the true riches?’ It would be pointless to try. The result would be entirely predictable. The man who has failed the lesser test is not going to succeed in the greater test. If earthly riches have corrupted him, then heavenly riches which are of far greater value will certainly corrupt him. Thanks be to God that those who are found worthy to receive eternal life are given a stability which will never let them fall.
Salvation is by grace alone, through faith, but it can never fail to take away covetousness, and to begin the process of putting it to death. The work of sanctification will be completed at death, and so, in the world to come, covetousness will have been completely eliminated from the hearts of God’s people. But even now that work has begun, and the changed heart of the Christian proves itself by producing good works, amongst which are works of kindness and generosity to those in need. It is a God given opportunity to be faithful.