The teaching that Jesus wants to give us here concerns wealth, and Luke, the evangelist of the poor, acts as his spokesman. The term “mammon” is an Aramaic word which means material goods, but Jesus is using it here in a negative sense, that is, as the embodiment of treasures which can take the place of God in people's hearts.
The danger with wealth is that people can fall in love with it to the point that they put all their strength and time into keeping and increasing it. It becomes an idol to which everything is sacrificed. This is why Jesus compares it to a master who is so demanding that he doesn't admit anything or anyone else. This explains the need to make a choice without compromises.

«No servant can serve two masters. He will either hate one and love the other, or be devoted to one and despise the other. You cannot serve God and mammon».

We shouldn't take Jesus' words as a condemnation of wealth as such, but of the exclusive place it can hold in the human heart.
He doesn't require absolute poverty of everyone; actually, some of his disciples were rich, like Joseph of Arimathea. What he requires is detachment from one's goods. Wealthy persons should not so much consider themselves as owners, but as administrators of the goods they possess, which belong primarily to God and are destined not only to a privileged few but to everyone.
Wealth is an excellent tool if used to serve those in need, to do good and to promote social wellbeing, not only by means of charitable works, but also by the management of a business. This is the only way to use our goods without becoming enslaved by them.
Accumulating riches for ourselves always poses a great risk. We know from our own personal experience and from history that attachment to the goods of this world can corrupt and distance us from God. Consequently, we should not be surprised by the alternative Jesus resolutely puts before us: either God or riches.

«No servant can serve two masters. He will either hate one and love the other, or be devoted to one and despise the other. You cannot serve God and mammon».

How can we live this Word of Life?
Besides clarifying for us the relationship we should have with wealth, these words, like every word of God, have many things to tell us. Jesus is not offering us the alternative of choosing God or mammon. He says clearly that it is God whom we must chose in life.
Perhaps we have not done this yet. Perhaps we have mixed a little faith in him, a few religious practices and a certain love for our neighbor with many other riches, great or small, which fill our hearts.
If we take a close look at ourselves we will be able to see if what matters most to us is work, family, studies, success, health or one of the many other things in life which we love for themselves or out of self-interest, ignoring God completely.
If this is the case, our hearts are already enslaved; our lives are centered on idols incompatible with God.
What should we do then? We must decide and tell God that we want nothing else but to love him with all our hearts, our minds, our strength. And then we must strive to fulfill this resolution which is not difficult if we do it moment by moment – now, in the present moment of our lives, loving everyone and everything out of love for God alone.

Chiara Lubich