"8 for at one time you were darkness, but now you are light in the Lord. Walk as children of light 9 (for the fruit of light is found in all that is good and right and true), 10 and try to discern what is pleasing to the Lord. 11 Take no part in the unfruitful works of darkness, but instead expose them. 12 For it is shameful even to speak of the things that they do in secret. 13 But when anything is exposed by the light, it becomes visible, 14 for anything that becomes visible is light. Therefore it says,
“Awake, O sleeper,
and arise from the dead,
and Christ will shine on you.”"
The AV rendering of 13 is somewhat difficult to understand, but the meaning is something like this: 'Let your lives show, by contrast, how dreary and futile these things are. For light is capable of showing up everything for what it really is. It is even possible for light to turn the thing it shines upon into light also'. Handley Moule paraphrases it as follows:
'You are light in the Lord: use this character upon the surrounding moral darkness, in order to the rescue of its victims, that they also may become light. Nothing but light will do this work: no conquest over darkness, literal or spiritual, is possible except to light. And one evidence of this is that every such real conquest results in the subjects of darkness becoming now subjects of light, becoming light.'
'You are light', Paul is saying, 'keep your light, then, but shine far into the dark. And then other men, as already you, shall become light in the Lord.' It is important to see the implications of this, in terms of the evangelistic power of a holy life. What is meant by saying this can be explained by reminding ourselves that there are two ways of looking at holiness. One is to think of it in terms of the devastating challenge and summons it presents to us to be holy as God is holy - a frightening and off-putting challenge indeed , as we may see from the way in which the first disciples reacted to the call to take up the Cross and follow Jesus.
But it is very impressive to see how, after Pentecost, their attitude was very different: then, they rejoiced that they were counted worthy to suffer shame for the Lord Jesus. That was the difference, and in that difference their lives were indeed transformed, and they were immensely attractive people who drew others to Christ by the very quality of their lives.