Our business is to present that which is timeless (the same
yesterday, today, and tomorrow [Hebrews 13:8]) in the particular language of our own age. The bad preacher does exactly the opposite: he takes the ideas of our own age and tricks them out in the traditional language of Christianity. Thus, for example, he may think about the Beveridge Report [on the social security system in Britain] and talk about the coming of the Kingdom. The core of his thought is merely contemporary; only the superficies is traditional. But your teaching must be timeless at its heart and wear a modern dress.
C.S. Lewis, "Christian Apologetics" (1945) included in God in the Dock (Eerdmans, 1970) 93-94.