When you read the Great Commission in Matthew 28:19-20 or its equivalents in Mark 16:15; Luke 24:47; John 20:21; and Acts 1:8, do you ever wonder what it is exactly that God wants us to SAY when we share the gospel? Fret no more: the answer is in Acts 10:42-43:
"And he ordered us to preach to the people and solemnly to testify that this is the One who has been appointed by God as Judge of the living and the dead. Of Him all the prophets bear witness that through His name everyone who believes in Him receives forgiveness of sins." (NASB)
This sums up what Peter said in Acts 2:22-36 on Pentecost Day; in 3:13-26 in the temple near the Beautiful gate; in 4:10-12 and in 5:30-32 to the Jewish religious leaders in council; explains what the scattered Christians preached in Acts 8:4 and what Philip said in Acts 8:5 in Samaria, in 8:35 to the Ethiopian eunuch, and in 8:40 in Azotus and other cities en route to Caesarea; and what Saul preached in Acts 9:22, 28. Indeed as Paul later wrote: "For we do not preach ourselves but Christ Jesus as Lord.." (2 Corinthians 4:5) - what exactly did he mean? Acts 10:42-43 gives the answer.
Indeed, if in our conversation with non-Christians, we do not talk about the work of salvation that Jesus has wrought for us, we are not sharing/preaching/telling the gospel. We must not become too concerned with the mechanics of how to "get" a non-Christian to "accept" Christ. All that is not part of the gospel but merely a means to help the non-Christian engage with what he hears. In Acts 10, Peter had not even gone to issue an invitation or challenge before the Holy Spirit fell upon his Gentile listeners and brought them to faith.
Acts 10:42 also makes clear that sharing the gospel is an imperatival activity. It has been commanded of Christians by God himself and hence a duty that we must not neglect. May the Lord help me to be faithful in proclaiming his good news.