“The light of the body is the eye: if therefore thine eye be single, thy whole body shall be full of light.
But if thine eye be evil, thy whole body shall be full of darkness. If therefore the light that is in thee be darkness, how great is that darkness! Matthew 6:2-23 KJV
We find in Proverbs 20:27 where man’s spirit is compared to a lamp: “The spirit of a man is the lamp of the Lord, searching all the inner depths of his heart” (NKJV).
The human spirit can have certain knowledge of its condition and state in reference to God and to salvation. This helps us to understand the Lord’s teaching because we can see a parallel between the spirit and the eye. We realize that as the eye is to the body, the spirit of man is to his soul. Just as your eyes perceive material things, your spirit can perceive spiritual truths.
We all know that the physical eyes can see sharply only if the vision is focused. If our eyes are not focused, we have a blurred vision.
The same is true in the spiritual realm. When Jesus said, ‘If your eye is good,’ He means, ‘If your eye is single.’ That is the translation you find in the King James Bible.
If you are going to see anything spiritually, then your vision must be single. The word ‘single’, applied spiritually, means singleness of devotion, singleness of attention, singleness of heart.
The heart is sometimes equivalent to the eye in the Scriptures. To ‘set the heart’ and to ‘fix the eye’ on something are parallel expressions. An example of this is found in Psalm 119.
Psalm 119:10: With my whole heart I seek you; do not let me stray from your commandments.
Psalm 119:15: I will meditate on your precepts, and fix my eyes on your ways.
In the same way, Jesus passes from the importance of having our heart in the right place in Matthew 6:21 to the importance of having an eye that is single in the following verse (v. 22).
If you are going to see anything clearly in the spiritual life, you must focus totally upon God. Your eye must be single.
Singleness of the eye and heart means that you set your attention upon God for the purpose of doing His will. This is a fundamental principle of spiritual vision.