Unlike Paul, Peter and the others were designated to be the apostles to the Jews.
But on the contrary, seeing that I had been entrusted with the gospel to the uncircumcised, just as Peter had been to the circumcised (for He who effectually worked for Peter in his apostleship to the circumcised effectually worked for me also to the Gentiles), and recognizing the grace that had been given to me, James and Cephas and John, who were reputed to be pillars, gave to me and Barnabas the right hand of fellowship, so that we might go to the Gentiles and they to the circumcised. (Galatians 2:7-9)
The apostles were carrying the message that the Jews were to have one final washing (baptism) with water. The story of the woman at the well explains that there was a water that satisfied after one drink leaving her never to be thirsty again. Similarly, the baptism that the apostles were giving was demonstrating a washing that would never need to be repeated again.
Therefore let all the house of Israel know for certain that God has made Him both Lord and Christ—this Jesus whom you crucified.” Now when they heard this, they were pierced to the heart, and said to Peter and the rest of the apostles, “Brethren, what shall we do?” Peter said to them, “Repent, and each of you be baptized in the name of Jesus Christ for the forgiveness of your sins; and you will receive the gift of the Holy Spirit. (Acts 2:36-38)
They heard was about a new way of salvation which was and continues to be Jesus Christ and Him alone!
For the promise is for you and your children and for all who are far off, as many as the Lord our God will call to Himself.” And with many other words he solemnly testified and kept on exhorting them, saying, “Be saved from this perverse generation!” So then, those who had received his word were baptized; and that day there were added about three thousand souls. (Acts 2:38-41)
Sacrifices and offerings used to be the normal way to achieve forgiveness. It was called atonement and it only covered over sins until the following year. Jesus was to be their new source of forgiveness. His way is called propitiation which means to completely satisfy the payment for sin. It doesn’t just temporarily cover it over anymore!