Acts 2:37-41

Now when they heard this, they were cut to the heart [with remorse and anxiety], and they said to Peter and the rest of the apostles, “Brothers, what are we to do?” And Peter said to them, “Repent [change your old way of thinking, turn from your sinful ways, accept and follow Jesus as the Messiah] and be baptized, each of you, in the name of Jesus Christ for the forgiveness of your sins; and you will receive the gift of the Holy Spirit. For the promise [of the Holy Spirit] is for you and your children and for all who are far away [including the Gentiles], as many as the Lord our God calls to Himself.” [Is 57:19; Joel 2:32] And Peter solemnly testified and continued to admonish and urge them with many more words, saying, “Be saved from this crooked and unjust generation!” So then, those who accepted his message were baptized; and on that day about 3,000 souls were added [to the body of believers].