2 But what means it, that He says they are “friends of the mammon of iniquity”? What is “the mammon of iniquity”? First, what is “mammon”? For it is not a Latin word. It is a Hebrew word, and cognate to the Punic language. For these languages are allied to one another by a kind of nearness of signification. What the Punics call mammon, is called in Latin, “lucre.” What the Hebrews call mammon, is called in Latin, “riches.” That we may express the whole then in Latin, our Lord Jesus Christ says this, “Make to yourselves friends of the riches of iniquity.”
Some, by a bad understanding of this, plunder the goods of others, and bestow some of that upon the poor, and so think that they do what is enjoined them. For they say, To plunder the goods of others, is the mammon of iniquity; to spend some of it, especially on the poor saints, this is to make friends with the mammon of iniquity. This understanding of it must be corrected, yea, must be utterly effaced from the tablets of your heart. I would not that you should so understand it.
Give alms of your righteous labours: give out of that which you possess rightfully. For you cannot corrupt Christ your Judge, that He should not hear you together with the poor, from whom you take away. For if you were to despoil any one who was weak, yourself being stronger and of greater power, and he were to come with you to the judge, any man you please on this earth, who had any power of judging, and he were to wish to plead his cause with you; if you were to give anything of the spoil and plunder of that poor man to the judge, that he might pronounce judgment in your favour; would that judge please even you?
True, he has pronounced judgment in your favour, and yet so great is the force of justice, that he would displease even you. Do not then represent God to yourself as such an one as this. Do not set up such an idol in the temple of your heart. Your God is not such as you ought not to be yourself. If you would not judge so, but would judge justly; even so your God is better than you: He is not inferior to you: He is more just, He is the fountain of justice. Whatsoever good you have done, you have gotten from Him; and whatsoever good you have given vent to, you have drunk in from Him.
Do you praise the vessel, because it has something from Him, and blame the fountain? Do not give alms out of usury and increase. I am speaking to the faithful, am speaking to those to whom we distribute the body of Christ. Be in fear and amend yourselves: that I may not have hereafter to say, You do so, and you too do so. Yet I trow, that if I should do so, you ought not to be angry with me, but with yourselves, that you may amend yourselves. For this is the meaning of the expression in the Psalm, “Be angry, and sin not.” I would have you be angry, but only that you may not sin.
Now in order that you may not sin, with whom ought ye to be angry but with yourselves? For what is a penitent man, but a man who is angry with himself? That he may obtain pardon, he exacts punishment from himself; and so with good right says to God, “Turn Your eyes from my sins, for I acknowledge my sin.” If you acknowledge it, then He will pardon it. You then who have done so wrongly, do so no more: it is not lawful.
Source: Sermons on Selected Lessons of the New Testament (New Advent)