When the Day of Pentecost had fully come, they were all with one accord in one place (Acts 2:1, NKJV).
The second chapter of Acts records a transformative moment, a pivotal point in the Scriptures. The Day of Pentecost was also known as the Feast of Weeks (Num. 28:26; Deut. 16:10), the Feast of Harvest (Exod. 23:16), and the day of the first fruits (Num. 28:26). This Pentecost would be a day of harvesting souls, the first fruits of the gospel. Many “first” things happened that day. (1) It was the first day of the week (Lev. 23:15-16). The first day of each week continues to call saints to assembled worship (Acts 20:7; 1 Cor. 16:2; Heb. 10:25). (2) The apostles preached the first gospel sermon opening the way to salvation. They used the keys of the kingdom, opening the door to salvation for sinners (Matt. 16:19; 18:18; Acts 2:40). (3) Sinners heard the plan of salvation for the first time. The apostles told those who believed the gospel to repent and be baptized to be forgiven of their sins (Acts 2:36-38). (4) The first gospel conversions took place. About three thousand did so and were saved (Acts 2:40-41). Christ still saves souls this way. (5) The first church came into existence that day. The church of Christ came into being. The Jerusalem church increased daily as the Lord added saved ones to His church (Acts 2:47). After Pentecost, Acts 2 records the first kingdom worship of the church (Acts 2:42) and the first acts of church benevolence (Acts 2:44-45). Acts 2 records the fulfillment of kingdom prophecies from Psalm 2, Isaiah 2, Joel 2, Daniel 2, and many more. Acts 2 has been called the hub of the Bible. Indeed.