Read Matthew 6.
In verses 19-21 Jesus talked about materialism. He concluded that section in verse 21 by saying, “For where your treasure is, there your heart will be also.”
In verse 24, he talked about money and concluded that verse by saying, “You cannot serve both God and money.”
Money and materialism are related ideas. So, when we read verses 22-23 about the eye being the lamp of the body, it seems clear that Jesus is still talking about money and materialism.
So what are verses 22-23 telling us about money/materialism?
Like windows, your eyes let inside whatever light or darkness is outside. If your eyes work properly, your whole body benefits because your eyes will tell you when to duck before you hit your head or when to step over a shoe that was left in the floor.
Without working eyesight, your whole body “will be full of darkness” (v. 23). You will stumble over everything and bang your noggin on anything that is hanging too low.
What determines “where your heart is” (v. 21) or whether you hate one master or love another? The answer is, whatever your eyes focus on.
The point of verses 22-23, then, is to be careful what holds your concentration. If you spend your time looking at catalogs of expensive watches, browsing elegant homes online that are for sale, looking at the pay scale for jobs LinkedIn for a job that will pay more than yours does, or test-driving new cars all the time, you will start to treasure money and material things.
If you focus on material things and money, that focus both shows what you love but also feeds that love.
If you focus on Jesus, however, your love will change, too. You will think less about expensive new shoes and more about how to serve the Lord.
So, watch what you watch–that’s the message of Matthew 6:19-24.