Proverbs 15:30 The light of the eyes rejoices the heart: and a good report makes the bones fat. 

‘The light of the eyes rejoices the heart: and a good report makes the bones fat.’ Righteousness rejoices the heart, and the good news is healthful.

‘Light of the eyes.’ Matthew 6:22 and Luke 11:34 state that the light of the body is the eye: if therefore thine eye be single, thy whole body shall be full of light; but when thine eye is evil, thy body also is full of darkness.

The Greek word luchnos, meaning, lamp fed by oil, burning for a time and then going out, translates as light 6 times (Mat. 6:22; Luke 11:34; 12:35; John 5:35; 2Pet. 1:19; Rev. 21:23) and candle 8 times (Mat. 5:15; Mark 4:21; Luke 8:16; 11:33, 36; 15:8; Rev. 18:23; 22:5). The Greek word haplous translates as single, simple, whole, good, and sound. If the eye is single and sound morally and free from any lusts, the whole body will be free from sin and morally sound and perfect. Light and darkness are used to contrast spiritual knowledge and spiritual blindness, and righteousness and sin (Mat. 4:16; Luke 1:79; John 1:5; 3:19; 8:12; 12:35, 46; 1Jn. 1:5-7; 2:8-11). If the eyes are full of adultery and lusts, the body will be dark and the life blind (2Pet. 1:9; 2:14; 1Jn. 2:15-17; Rev. 3:17-18).