"The time is fulfilled, and the kingdom of God is at hand; repent and believe in the gospel."--Mark 1:15 (ESV)
"Now when they heard this they were cut to the heart, and said to Peter and the rest of the apostles, "Brothers, what shall we do?" And Peter said to them, "Repent and be baptized every one of you in the name of Jesus Christ for the forgiveness of sins, and you will receive the gift of the Holy Spirit."--Acts 2:37-38 (ESV)
My church has been going through a series on evangelism recently, and so I have been looking for Bible passages which model proper evangelism. I have been surprised to see not only how many times the Bible exhorts unbelievers to be saved, but also by the simplicity of the message preached.
In Acts 2, Peter preached a sermon which can be read (and, I infer was preached) in just a few minutes. His oration was not eloquent nor was it long--but through it he convicted thousands of their need for salvation. In Mark 1:15, Jesus commanded unbelievers to "repent and believe" because "the kingdom of God is at hand"--a very simple and straightforward exhortation. Obviously, the evangelistic message is not a complicated message.
In my opinion, though, modern Christianity has overcomplicated evangelism. For example, a few weeks ago, I attended a Christian concert with an evangelistic message. A pastor spoke at great length on how life is only found in Jesus--a good message. However, it took him forty-five minutes to get to the main point: "Repent and believe." In my mind, novel techniques and wordplay and eloquent messages have oftentimes seemed essential to evangelism. However, the Bible testifies to the contrary--that the gospel is not complicated and the message most needed by the world is simple.
As we look for evangelistic opportunities, let's keep the simplicity of the gospel in mind.