What is God's requirement for salvation (GRFS)?
I read that the term kerygma came to refer to the essentials of the gospel message at sometime after the word was used in the New Testament.
But this is an important topic. I've taken to prayerfully pointing out to preachers when they do a 'challenge' at the end of the message and leave out the resurrection and sometimes the crucifixion (trying to come up with a name for it. When I was a kid, there were more 'altar calls', but now they keep the people in the connected seats that replaced the pews.)
When Paul explained the gospel in I Corinthians 15, he included the fact that Christ died for our sins, according to the scriptures, that He was buried, and that he rose again the third day according to the scriptures. Then he starts talking about witnesses, then includes himself and goes into other topics.
Luke 24 contains a good summary from the mouth of Christ, that the Messiah had to suffer, be buried, and rise again from the dead according to the scriptures, and that repentance and remission of sins are to be preached in His name to all nations. He said, 'ye are witnesses of these things.'
In my own lifetime, I've seen evangelism and altar calls go from preaching the cross and (hopefully) the resurrection, with an emphasis on Christ dying for our sins... to a little sermon add on about religion being supposedly bad and relationship good.... so why don't you repeat this prayer to receive Jesus--who I haven't told you about today.
It's as if repeating a prayer to 'receive Christ' is the same as receiving Christ. I would say this approach is based on John 1 where it says that as many as received Him received power to become the sons of God. I'd say that's an influence on the phrase 'receive Christ.' But I think the modern prayer is based on 'monkey see, monkey do', relying on ritual instead of knowledge of scripture, and the tendency of evangelicalism to be reductionist. Preachers grew up with the sinner's prayer ritual, and learned it as it gradually got reduced to exclude the gospel, as it became a little tag on after a message that does not preach the risen Christ.
The sinner's prayer as we know it is about 70 years old. Billy Graham used to preach the death, and resurrection of Christ. He had prayer counselors to counsel people after a meeting, going through points of the gospel, and they had a little prayer at the end of their booklet to serve as a confession of faith where the individual confessed himself as a sinner, acknowledged faith in Christ as Lord and that He died for his (or her) sins and rose again. Many evangelicals adapted the ritual of repeating the prayer as the part that saves instead of the gospel part.
In line with the so-called 'Great Commission' passage in Matthew 28 and the preaching and practice of apostles like Peter and Paul, I believe it is appropriate to offer someone baptism after presenting the gospel, at least if they are ready. I notice Paul did not offer baptism at the Aeropagus while dealing with pagans when he had to start with explaining who God is, different from his ministry to Jews. But he did baptize a jailor in Philippi, no doubt after sufficient explanation.
I could go into evangelical concepts regarding salvation being in internal supernatural transformation versus the 'intellectual' aspect of affirming and believing points of the gospel and historical facts, but tat would make my message even longer.