What does Acts 3:23 mean?

Peter is talking to a crowd of Jews in Solomon's Portico on the Temple Mount; likely, there are proselytes there, as well. They are there for the 3 p.m. prayers at the temple (Acts 3:1). They consider themselves followers of God and heirs of Abraham, Isaac, and Jacob. What they need to realize is that in order to remain Abraham's heirs, they need to follow Jesus, as well.

"That prophet" is Jesus. In Deuteronomy 18:15, Moses promised the Israelites that another prophet would come and take his place. A prophet is someone who receives a message from God and passes it on to His people. Sometimes that message is instructions, like how to build the tabernacle (Exodus 25:9). Sometimes, it's a warning, like the Old Testament books of the prophets' record. Other times, it's images of the future, like in Daniel 7. Jesus did all of this throughout His ministry, being careful to speak what God the Father told Him to (John 12:49).

The Jews in Peter's audience knew to look for "the prophet," but they didn't know that prophet was Jesus of Nazareth. Now, they're being told that to remain true Jews, they have to listen to a man whom the Sanhedrin contrived to have crucified. They can't just call Jesus a good teacher or even a miracle worker. Peter tells them, "The God of Abraham, the God of Isaac, and the God of Jacob, the God of our fathers, glorified his servant Jesus" (Acts 3:13). Jesus said Abraham, Isaac, and Jacob and all the prophets will enter God's kingdom, but those who do not accept Him will be cast out (Luke 13:28).

Fortunately, from this crowd, thousands of men plus women do believe (Acts 4:4). They understand that Jesus is the Messiah and following Him is the fulfillment of what Judaism promised.