This is the first of about 30 speeches in Acts and one of the most important. It marks the beginning of the Christian church. It is a typical example of the preaching of the apostles.
The apostles proclaimed:
that the Old Testament promises came true in the life, death, and resurrection of Jesus, the promised Messiah;
that the apostles were eyewitnesses of the public ministry of Jesus and were his chosen representatives;
that people must turn away (repent) from their sins and trust in God through Christ; and
that salvation and the presence of the Holy Spirit are promised to those who have a positive response to this message of the gospel.
This basic message repeats in the sermons of chapters 3, 4, 5, 8, 10, and 13. The same themes characterized the apostle Paul's preaching (see 1 Corinthians 15:3–9). The apostles all repeated this message when preaching to both Jews and non-Jews (Gentiles) throughout the world around the Mediterranean Sea. All people must turn away (repent) from their sins and turn to God by trusting in Jesus Christ.