"The light of the body is the eye: therefore when thine eye is single, thy whole body also is full of light; but when thine eye is evil, thy body also is full of darkness. Take heed therefore that the light which is in thee be not darkness." - Luke 11:34-35
Then spake Jesus again unto them, saying, I am the light of the world: he that followeth me shall not walk in darkness, but shall have the light of life. - John 8:12
The function of light is to shine into darkness. Jesus said that he is the light of the world, and whosoever follow him, shall have no darkness in life.
In Luke 11:34, Jesus also teaches that the light of our body is the eye. He is talking about our eye-gate, one of the two sensory organs that allow information to reach our mind. If we are able to keep our eye-gate holy, so that it is single, which means simple, and not looking at things that are unclean, then our inside should have no darkness.
Jesus is not teaching us to check into others’ eyes, and to judge how spiritual they are. He is warning us about the lust of the eyes, and we need to stay away from the unclean information that is so profuse around. All sort of information are indeed at our finger tips. There are movies, music CD, CD, TV programs, even information or pictures from newspaper/magazines/catalogue are not meant for Christians, and loads of pornography can be accessed through interment. The production of pornography in USA increased by 1000% in the last 10 years. Why? Because through lust, the world is letting go their eye-gates.
Many teachings in the Bible warns against the lust of the eyes. It is not a sin for King David to accidentally look at the naked Bathsheba; however, when he took the second look, the movement of sin started its course.( 2 Samuel 11). Take heed of what we look at twice, keep our eyes single - so single, so focused that they only see Jesus.