I was reading Matthew six and came upon a verse (among many), that I have wondered about. I did some research and found this piece by John Piper. I like this explanation the best so I wanted to share it with you.
What Is the “Bad Eye” in Matthew 6:23?
August 17, 2005 by John Piper Scripture: Matthew 6:23 Topic: Money Series: Taste & See Articles
The fighter verse (church-wide memory verse) for August 14, 2005 was difficult to understand. It seems to dangle in the Sermon on the Mount with little connection to what goes before and after: “The eye is the lamp of the body. So, if your eye is healthy, your whole body will be full of light, 23 but if your eye is bad, your whole body will be full of darkness. If then the light in you is darkness, how great is the darkness!” (Matthew 6:22-23).
Before it: the familiar saying about not laying up treasures on earth: “Do not lay up for yourselves treasures on earth, where moth and rust destroy and where thieves break in and steal, 20 but lay up for yourselves treasures in heaven, where neither moth nor rust destroys and where thieves do not break in and steal. 21 For where your treasure is, there your heart will be also” (Matthew 6:19-21).
After it: the equally familiar saying about not serving God and money: “No one can serve two masters, for either he will hate the one and love the other, or he will be devoted to the one and despise the other. You cannot serve God and money” (Matthew 6:24).
Therefore, the sayings before and after Matthew 6:22-23 deal with treasure or money.
In fact, the first would flow really well into the second if we simply left out the intervening verses 22-23. The gist would be “Treasure God in heaven, not money on earth . . . because you can’t serve two masters, God and money.” So why does Jesus link these two sayings about money and God with a saying about the good eye and the bad eye?
The key is found in Matthew 20:15. Jesus had just told the parable of the workers in the vineyard. Some of them had agreed to work from 6 am to 6 pm for a denarius. Some the master hired at 9 am. Others at noon. Finally some he hired at 5 pm. When the day was done at 6 pm he paid all the workers the same thing—a denarius. In other words, he was lavishly generous to those who worked only one hour, and he paid the agreed amount to those who worked twelve hours.
Those who worked all day “grumbled at the master of the house” (Matthew 20:11). They were angry that those who worked so little were paid so much. Then the master used a phrase about “the bad eye” which is just like the one back in Matthew 6:23. He said, “Am I not allowed to do what I choose with what belongs to me? Or do you begrudge my generosity?” (Matthew 20:15).
Unfortunately that last clause is a total paraphrase, not a translation. “Or do you begrudge my generosity” is a very loose paraphrase of “Or is your eye bad because I am good (ë ho ophthalmos sou ponëros estin hoti egö agathos eimi?)” The “bad eye” here parallels the “bad eye” in Matthew 6:23.
What does the bad eye refer to in Matthew 20:15? It refers to an eye that cannot see the beauty of grace. It cannot see the brightness of generosity. It cannot see unexpected blessing to others as a precious treasure. It is an eye that is blind to what is truly beautiful and bright and precious and God-like. It is a worldly eye. It sees money and material reward as more to be desired than a beautiful display of free, gracious, God-like generosity.
That is exactly what the bad eye means in chapter six of the Sermon on the Mount. And that meaning gives verses 22-23 a perfect fitness between a saying on true treasure (vv. 19-21) and the necessity of choosing between the mastery of God and the mastery of money (vv. 24).
So the flow of thought would go like this: Don’t lay up treasures on earth, but lay up treasures in heaven. Show that your heart is fixed on the value that God is for you in Christ. Make sure that your eye is good not bad. That is, make sure that you see heavenly treasure as infinitely more precious than earthly material treasure. When your eye sees things this way, you are full of light. And if you don’t see things this way, even the light you think you see (the glitz and flash and skin and muscle of this world) is all darkness. You are sleepwalking through life. You are serving money as a slave without even knowing it, because it has lulled you to sleep. Far better is to be swayed by the truth—the infinite value of God.