Here is the "good news" which Paul preached in the synagogues of the Jews:
"And straightway he preached Christ in the synagogues, that he is the Son of God...proving that this is the very Christ" (Acts 9:20,22).
That was the same gospel which Paul continued to preach to the Jews:
"And Paul, as his manner was, went in unto them, and three sabbath days reasoned with them out of the scriptures, Opening and alleging, that Christ must needs have suffered, and risen again from the dead; and that this Jesus, whom I preach unto you, is Christ" (Acts17:2,30).
That is the same message that Apollos preached to the Jews:
"For he mightily convinced the Jews, and that publicly, shewing by the scriptures that Jesus is Christ" (Acts18:28).
On the day of Pentecost Peter used the facts concerning the Lord Jesus' death and resurrection in order to prove that He is the promised Messiah and then he summed up his discourse by saying:
"Therefore let all the house of Israel know assuredly, that God hath made the same Jesus, whom ye have crucified, both Lord and Christ" (Acts 2:36).
Dr. Stanley D. Toussaint, Senior Professor Emeritus of Bible Exposition at Dallas Theological Seminary (Acts 2), writes the following commentary on Acts 2:36:
"Here is the conclusion to Peter's sermon. The noun 'Lord', referring to 'Christ', probably is a reference to Yahweh. The same word 'kyrios' is used of 'God' in verses 21, 34, and 39 (cf. Phil. 2:9). This is a strong affirmation of Christ's deity" (The Bible Knowledge Commentary; New Testament, ed. Walvoord & Zuck, [ChariotVictor Publishing, 1983], 359).
The Jews who believed that Jesus is Christ, God come in the flesh, were "born of God". Dr. Zane Hodges, past Chairman of of the New Testament Department at Dallas Theological Seminary, writes the following in regard to Peter's words:
"Peter concludes his address with the assertion that 'God has made this Jesus, whom you have crucified, both Lord and Christ' (2:36). His hearers then reply, 'Men and brethren, what shall we do?' (2:37). But such a reaction presumes their acceptance of Peter's claim that they have crucified the one who is Lord and Christ. If this is what they now believe, then they were already regenerated on Johannine terms, since John wrote: 'Whoever believes that Jesus is the Christ is born of God' (1 John 5:1; cf. John 20:31)" [emphasis added] (Hodges, The Gospel Under Siege, 101).
Here are the verses to which Hodges makes reference:
"Whosoever believeth that Jesus is the Christ is born of God...Who is he that overcometh the world, but he that believeth that Jesus is the Son of God?" (1 Jn.5:1,5).
On the day of Pentecost those who believed the "good news" that Jesus is the Christ, the Son of God, were "born of God" and saved. And the apostle John confirmed that fact:
"Jesus performed many other signs in the presence of his disciples, which are not recorded in this book. But these are written that you may believe that Jesus is the Messiah, the Son of God, and that by believing you may have life in his name" (Jn.20:30-31).