"The lamp of the body is the eye. If therefore your eye is good, your whole body will be full of light. But if your eye is bad, your whole body will be full of darkness. If therefore the light that is in you is darkness, how great is that darkness! "No one can serve two masters; for either he will hate the one and love the other, or else he will be loyal to the one and despise the other. You cannot serve God and mammon. Matthew 6:22-24
It is imperative to understand that Jesus’ reference to the eye (v.22-23) as illustrative rather than being about one’s physical eyes. A simple way to understand Jesus’ warning is to think of what it means to have an eye for, or to whatever. For example, automobile enthusiasts have an eye for cars. Cat lovers have an eye for felines. I trust you get the point.
Remember the context (v.19-20) about investing oneself and one’s possessions either in heavenly or earthy pursuits. Jesus is saying what one invests oneself in and one’s possessions will be determined by where one’s heart is (v.21), and synonymously by what one has an eye for (v.22-23).
Putting it all together, Jesus is saying, Where your heart is (v.21), and what you have an eye for (v.22-23), determines what one values most.
Then in verses 23-24, Jesus drops the bomb that our hearts cannot truly be divided. We cannot love both heavenly and earthy things equally. We can and do love many good and God-ordained interests in this life (e.g., things from spouses and family, to hobbies and chocolate). But if we love any of these equally, much less more than we love God, we are are self-deceived.
We do well to routinely ask ourselves, “What do I have an eye for”?