At last, at the feast of Pentecost, fifty days after the passover, the promise of Jesus was fulfilled; the Holy Spirit came upon the disciples to fit them for the evangelization of the world. Acts 2:1-13. They were all together in one place; there was a sound as of a rushing, mighty wind; cloven tongues, like tongues of fire, sat upon each one of them; they were all filled with the Holy Spirit, and began to speak with other languages as the Spirit gave them utterance. When the crowd came together to see the wonderful thing that had happened, Peter preached the first sermon of the Christian Church. Vs. 14-36. At the preaching of Peter three thousand persons were converted; the campaign of world conquest had begun. Vs. 37-42.

The campaign from the beginning was a campaign of witnessing, in accordance with Jesus' command. Acts 1:8. The Christian Church was to conquer the world, not by exhorting men to live a certain kind of life, but by bringing them a piece of news. The Son of God, said the Christian missionaries, died on the cross and then rose again. That was the good news that conquered the world. Christianity from the beginning was a way of life, but it was a way of life founded upon a piece of news, a way of life founded upon historical facts. The meaning of the facts was not revealed all at once, but it was revealed in part from the very beginning, and throughout the Apostolic Age the revelation came in greater and greater fullness, especially through the instrumentality of Paul.

The life of the Early Church in Jerusalem was in some respects like that of the Jews. The disciples continued to observe the Jewish fasts and feasts and were constantly in the Temple. But a new joy animated the company of believers. Their Lord was indeed taken from them for a time, and they did not know when he would return, but meanwhile he was present with them through his Spirit, and already he had saved them from their sins.

Even in external observances the believers were distinguished from the rest of the Jews. Entrance into their company was marked by the sacrament of baptism, which signified the washing away of sin; and their continued fellowship with one another and with the risen Lord found expression in the sacrament of the Lord's Supper, which commemorated the atoning death of Jesus. There were also common meals. And those who had property devoted it, in a purely voluntary way, to the needs of their poorer brethren. The disciples attended diligently, moreover, to the teaching of the apostles, and engaged constantly in prayer.