“Haughty eyes and a proud heart, the lamp of the wicked, are sin.”
Every person operates their life according to a belief system. They see the world through a lens that is shaped by the assumptions and beliefs they hold in their heart. This is what “the lamp” means in this verse.
If the beliefs that you hold in your heart are in alignment with God’s truth, then you will operate your life with clarity and wisdom. This is when your inner “lamp” is clear and right. But if you operate your life with beliefs that are arrogant and selfish, then you will operate your life in a way that is wicked and sinful. This is when your inner “lamp” is dark and distorted.
In the Sermon on the Mount, Jesus communicated the same truth: “The eye is the lamp of the body. So, if your eye is healthy, your whole body will be full of light, 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)
"The eye is the lamp of the body" refers to the way you see things. An eye that is "healthy" means clarity of vision that produces wise decisions; an eye that is "bad" means distortion of vision that produces unwise decisions. Jesus is teaching that it is enormously important to understand the way you look at yourself, other people, and the situations you experience. You see life through a lens, and sometimes that lens helps you see clearly and accurately, and sometimes it darkens and distorts.
We could paraphrase it this way: “The eye refers to the reference points you use for the way you see the world, make decisions, and live your life.”
If your eye is healthy (clear vision guided by Truth), then your life is full of light and you can deal with people and situations according to what is actually happening. But if your eye is bad (impaired vision because Truth is rejected), then your life is full of darkness and you will react to people and situations based on a distorted perspective.
It is the dark, distorted lens that is described in Proverbs 21.4 that is quoted above: “Haughty eyes and a proud heart, the lamp of the wicked, are sin.” Clarity of vision determines quality of response.
Through what lens do you see the world?