Not only may believers be tempted to become like the world in order to reduce their distinctiveness, but there is another way of avoiding persecution which is to hide the fact that we have come to Christ altogether. The first illustration here is about sunlight.
How remarkable that Christ should compare his people to the sun shining in the sky! But although the world loathes to hear this, that is the true situation. The world is in darkness and has no light whatsoever without Christians to speak to it of the Lord. Despite all their enquiries and searches after truth, and philosophical theories, and time, and effort, they remain in the darkness. If they want light, they are obliged to come to the one source they do not want to come to by nature. This is more than proud human nature can tolerate.
What great responsibility God has given to his people! The sun shines in the sky because of the light producing process that goes on relentlessly inside it. The city built on a hill is visible simply because it exists and has been placed there. But the people of God act as a light and as a city on a hill, because they consciously and deliberately live for God in the sight of the world around them. As they do so, they are to some extent aware of the effect of their lives on those who see them. They sense the impact they have on other people’s consciences, for the witness spoken of here is first and foremost a witness which has a moral impact. At any moment they can hold back or they can press forward in their witness, depending on what effect they wish to have. Those who wish to honour the Lord and to be fruitful for him in this life will strain every sinew to glorify Christ in their lives. They hope for fruit from their lives which endures to eternity in the form of men and women brought to salvation in Christ.