"For ye were sometimes darkness, but now are ye light in the Lord: walk as children of light: for the fruit of the Spirit is in all goodness and righteousness and truth" (Ephesians 5:8,9)
When Christ came, light came. He said, "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), and again, "Ye are the light of the world" (Matthew 5:14).
The matter of walking in the light and being good lights is very practical. It involves goodness, righteousness and truth for Paul wrote that these are the fruit of the Spirit.
Goodness is a kindly consideration of others. In Acts 10:38 it is stated that Jesus went about doing good. The Christian life is not merely a question of being good, but of doing good. Righteousness is the doing of right things. A friend said to me, "I spend hours each day just keeping my business honest." There should be nothing deceptive nor under-handed in the Christian's daily life. All his activities should glorify God. Truth implies the acquiring and practicing of truth. "Thou desirest truth in the inward parts," said the Psalmist (Psalm 51:6).
The outcome will be the approving of that which is acceptable to the Lord, and the reproving of the unfruitful works of darkness (Eph. 5:10,11).
"Do all things without murmurings and disputings: that ye may be blameless and harmless, the sons of God, without rebuke, in the midst of a crooked and perverse nation, among whom ye shine as lights in the world; holding forth the word of life" (Phil. 2:14-16)
(Dr. R. H. Belton)