NOTES for Mat 6:16-24
Have you ever, say, gone swimming while vacationing at the seaside and left a bag with money on the beach? You splash around in the water, but something spoils your pleasure: you keep looking back at your things... "Where your treasure is, there your heart will be also."
Of course, this is a very primitive illustration of Jesus' words, but are you and I really such complicated beings? The same mechanism for distributing our attention operates in more "spiritual" situations too. Of course, earthly matters are important, and they must be given attention. Will we be able each time to keep within ourselves the right vertical order of what matters most, where God, the Spirit, and love are above all?
The following words of Christ about God and mammon, or wealth, speak about the same thing. Jesus is not against wealth or well-being. He says that they must not be placed at the center of our service and attention; that place must be reserved for God.