There’s no way to know exactly how many people heard the Spirit roar like a rushing wind, or how many people saw twelve men who shone like the sun, or how many people heard Peter preach the gospel with a flaming tongue on the day of Pentecost. All we know is that the Holy Spirit consecrated three thousand souls to the Lord in baptism, collected them into the church, and began conforming them to the image of Christ.
Three thousand seems like a lot of people to us, but it was a small number compared to the thousands upon thousands who had gathered in Jerusalem for Pentecost.
For devout Jews, Pentecost was a time to celebrate the giving of the Law at Sinai, fifty days after the Passover and the Exodus from Egypt.
For disciples of Jesus, Pentecost is a time to celebrate the out-pouring of the Holy Spirit and the giving of the Gospel, fifty days after the true and better Passover and Exodus — the crucifixion of Jesus and his resurrection from the grave.
At the first Pentecost, the Lord God sounded the trumpet from the mountain.
At the last Pentecost, the Lord Jesus poured out the Spirit from heaven, and there came from heaven the sound of a rushing wind.
At the old Pentecost, the people broke loose and worshiped a golden calf.and the gospel was proclaimed to a solemn assembly, and the people praised God.
At the old Pentecost, three thousand were slain with the sword.
At the new Pentecost, three thousand were signed and sealed with the Spirit.
At the old Pentecost people were cut off from the community of God’s people.
At the new Pentecost people were cut to the heart and united to Christ and his church.
At the old Pentecost the Spirit wrote the Law on tablets of stone.
At the new Pentecost the Spirit wrote the Gospel on the hearts of men, women, and children.
In effect, on the day of Pentecost Peter stood up in the midst of the crowd and (like Moses) said, “Who is on the Lord’s side? Come to Jesus! The promise is for you and your children!”
And three thousand souls gathered around the apostles; they were baptized and added to their number that day — men, women, and children.
How did the apostles baptize so many people in one day?
They baptized individuals and their households. “The promise is for you and your children.”
Where did they find enough water in Jerusalem to immerse all those people?
There was no place in Jerusalem to immerse three thousand people. Nor was it necessary to find one. They administered baptism by sprinkling or pouring water on the people just as God promised would happen in the Law and the Prophets. “I will sprinkle clean water on you and you will be clean.” “I will pour out my Spirit.”