Take no part in the unfruitful works of darkness, but instead expose them. (ESV)
One of the biggest hindrances to people coming to faith in Jesus Christ is the fact that they have met "Christians." That is a harsh statement. However, I feel that it is fairly accurate. In fact, I feel that there have been times when I have been guilty of being such a hindrance. The Apostle Paul is making a very stark contrast between Christians and non-Christians. They are as different as darkness and light.
Christians are admonished to do two things in this verse. (1) Avoid the darkness, and (2) Expose the darkness. The problem is that many Christians are involved in falling back into the darkness. As a result, those who are in darkness are unable to see the light, because we are clouding it in the darkness of sinful behavior.
Consider the importance of avoiding darkness. How important is it really? I mean, just because someone calls themselves a Christian, but is involved in all kinds of darkness, is it really our business? I mean, after all, we don't want to judge them, do we? Listen to what Paul says to the church at Corinth:
1 Corinthians 5:11
 But now I am writing to you not to associate with anyone who bears the name of brother if he is guilty of sexual immorality or greed, or is an idolater, reviler, drunkard, or swindler—not even to eat with such a one. (ESV)
These are strong words, aren't they? Paul is so concerned with the integrity of our testimony among unbelievers that he does not want our light to be dimmed by associating with those who are claiming to be light while living in darkness. We are to avoid the unfruitful works of darkness. Things that hinder the powerful Gospel of Jesus Christ are unfruitful works of darkness. Tomorrow we will look at the second admonition of exposing the darkness.
Are people able to see the light of Christ shining in you? Or are you involved in works of darkness? Come to Jesus and repent of any darkness. He will forgive and restore you so that you can shine for him.