The Greek word being translated to "money" here is μαμωνᾶς (mamōnas). The word means, according to the lexicon, "mammon" or "treasure" or "riches."
Yes, it certainly can be translated to "money" - but that was not what Jesus was referring to. Why? Because money is a means of exchange. It is not bad in itself. It cannot be a "master" in itself.
Rather, what Jesus is referring to is materialism. This is the modern-day term used to describe "mammon."
"Mammon" or materialism is the desire to enjoy this physical world. It is the desire to enjoy these temporary physical bodies.
And why is this juxtaposed against serving God - "You cannot serve both God and materialism"?
Because materialism in essence is the expression of self-centeredness. The desire to please oneself. This is the pervading goal among the residents of the physical world.
And the pervading goal among those in the spiritual realm is quite the opposite: The residents of the spiritual realm seek to please the Supreme Being.
Yes, this is called love of God - and it is diametrically opposed to loving oneself.
Yet surprisingly, this teaching - that we have to love ourselves before we can love others - is being taught by ecclesiastical and secular teachers in modern society.
It is an erroneous teaching. To love oneself is self-centeredness, and this does not lead to loving others.
But coming to love and serve the Supreme Being - that will cause one to love others because we are all the children of the Supreme Being.
This was confirmed by Jesus when he said:
'Love the Lord your God with all your heart and with all your soul and with all your mind.' This is the first and greatest commandment. And the second is like it: 'Love your neighbor as yourself.'" (Matt. 22:37-40)
Love of God is connected to loving others. It is a pre-requisite. And loving God is the antithesis of loving oneself.
But doesn't it say "as yourself" so we need to love ourselves?
This is a self-centered, myopic approach. The verse is assuming we already care about ourselves. It is a foregone conclusion. It is already there. Not that we need to focus upon it even further.
This teaching was intended to take our attention off of ourselves - and put our love upon the Supreme Being and others instead of ourselves. But those who wish to interpret Jesus' teachings to accommodate their own desires would rather focus upon the "as yourself" of this instruction rather than the rest of it.
Such is the nature of self-centeredness.
Ones focus upon pleasing oneself is redirected to materialism. This is because our self-centeredness resulted in us being put within a physical body within the physical world. We became covered up by these physical bodies. So our self-centeredness becomes directed towards working to satisfy the physical body and those things the physical body is surrounded by.
This means the temporary things of this world. This means the desires for sensual pleasure, fame, wealth, a big house, a big family, to be the boss, to be the hero and so on. All of these things together are defined within the notion of materialism.
And should ones self-centered focus become directed towards these things - or any combination thereof - we will become the servant of materialism.
Yes - achieving all of the things of materialism requires work. It requires work to become wealthy or famous. It requires work to by the big house or get the big job. What is this work? It is service. We have to become the servant of materialism in order to capture the things of this world.
In other words, Jesus is discussing the ultimate choice we face between God or ourselves.
In the spiritual world the focus of attention is upon the Supreme Being. This focus is accompanied by loving service, because God is the most attractive and most lovable Person and loving service is how love is expressed. Our relationship with God is what we are searching for when we look for our perfect soul mate. The exchange of love with God and loving service to God is what we really seek when we seek pleasure.
Yet because He also gave us the freedom of choice whether to love Him, and since He is loving us unconditionally and thus kindly rewarding our wishes, when we chose our self-centered desires over loving Him, He granted us the ability to exercise that choice by our taking on these temporary physical bodies within the material world.
This doesn't mean we no longer have choice. While the physical world is ultimately not a place of pleasure but a place of suffering (diseases, old age, death and pain with short flashes of physical pleasure), we still have that choice whether to focus our attention upon Him or upon our own desires and wishes.
In reality, God has arranged this physical environment and our current physical body - reflecting a combination of our wishes and past decisions - so we do not have to see Him. He has arranged the body and our physical environment in such a way that His presence is invisible to us. This arrangement allows us the ultimate freedom to choose between God and our own desires: We can choose to ignore Him or we can choose to worship Him: It is our choice because love requires freedom and the Supreme Being enjoys the exchange of love.
Our situation within the physical world can be most readily understood by considering dreaming. When we dream, our bodies are lying in the same place in our bed, while our minds take us through illusory and temporary existences in different places. In our dreams we can play out our fantasies and our nightmares. In our dreams we can take on different personalities. One night we might be a wealthy man governing a big company. Another night we might be a poor woman working as a slave.
In each dream, we take on a situation, and we navigate the dreamscape with a particular dream character (one we temporarily identify with during the dream), our wishes and our decisions.
Once we awaken from the dream, we realize the whole thing was an illusion: The identity we identified with was temporary. The environment and situation we were in was temporary. Even though we identified with it as real during the dream, once awake, we realized the dream was just a temporary manifestation - an illusion of reality.
The temporary physical body we wear at the moment is practically similar to the dream, except it is one physical layer higher. While our gross physical body is tangible and real, it is still temporary. Here the illusion is that this is our permanent place, and we will become happy here somehow. The gross physical body is still a reflection of our desires and past activities, just as is the dream.
The changes that occur around us in the physical world accommodate our ongoing wishes, desires and past decisions. This is God's arrangement to accommodate our current choice of being away from Him.
The nature of our choice between God and materialism is that we can either focus upon God or we can focus upon ourselves. By focusing upon God and serving God we become fulfilled, because this is our innate spiritual position. By focusing upon ourselves, we become engrossed in self-centeredness and the requirements of materialism - which become our master.
Jesus is communicating that these two choices are mutually exclusive: We can't go both directions at the same time, because they are diametrically opposed.
(For a translation of Jesus' statements from the Gospel of Matthew without institutional sectarian influence, see the Gospels of Jesus - translated from the original Greek texts.)