How, then, should evangelism be defined? The New Testament answer is very simple. According to the New Testament, evangelism is just preaching the gospel, the evangel. It is a work of communication in which Christians make themselves mouthpieces for God’s message of mercy to sinners. Anyone who faithfully delivers that message, under whatever circumstances, in a large meeting, in a small meeting, from a pulpit, or in a private conversation, is evangelizing. Since the divine message finds its climax in a plea from the Creator to a rebel world to turn and put faith in Christ, the delivering of it involves the summoning of one’s hearers to conversion. If you are not, in this sense, seeking to bring about converstions, you are not evangelizing; this we have seen already. But the way to tell whether in fact you are evangelizing is not to ask whether conversions are known to have resulted from your witnes. It is to ask whether you are faithfully making known the gospel message.
– Evangelism & the Sovereignty of God (Downers Grove: IVP, 1961), p. 41.