First, they were devoting themselves to the apostles’ teaching. They were continually devoting themselves, i.e., it was the ongoing life of the Church, the new community of faith, the New Israel, to be continually devoting themselves to the oral proclamation of the Gospel. There was no New Testament. The teaching was the apostolic teaching, i.e., it was the foundation of the Tradition given through the ones Christ had appointed to be his representatives to build up and govern the Church.
The apostolic teaching was lifting the veil of the Old Testament, which was the only Bible the Church had at this point. It was lifting the veil because the apostles were doing what Christ has done in Luke 24, viz., beginning with Moses and all the Prophets, they were teaching in all the Scriptures the things concerning Jesus Christ. This was done through the apostolic authority, given them by Christ to be his witnesses.
The Church, which had just been constituted through a radical intervention by God in the Holy Spirit, was not devoting itself to seek new subjective experiences of the Spirit – trying to see the fire, the wind, and to speak in foreign languages. No, the people were devoting themselves to the teaching. There is no life in the Church without the continuous devotion to the public proclamation and instruction of the Word of God, as well as private study and growth in the same Word that is the pure milk that nourishes us unto salvation.
Second, they were devoting themselves to fellowship, i.e., koinonia. The Church was not an individualistic church, for there is no salvation without the common life of the body of Christ. There is no such thing as lone range Christianity. Under the authority of the shepherds whom Christ had appointed over his Church, they were continually devoting themselves to one another in fellowship.
Their fellowship was not merely a social event, although it involved that. It was more than just a club, it was actually a fellowship in which people concretely cared for one another, loved one another, and provided for the needs of one another. There is no Christianity without concrete expressions of love for one another in the body of Christ.
Third, they were continually devoting themselves to the breaking of the bread. In the New Testament, this is very specific language to refer to the Eucharist. Remember, Luke himself had already told us, in the first volume of his work (i.e, the Gospel of Luke) that in Emmaus, Christ revealed himself, opened the eyes of his disciples, and gave himself to them in the breaking of the bread.
From the very foundation of the Church on, the center of Christian worship has always been the Lord’s Supper, the mystical communion of the body and the blood of Christ, in which we are united to him and to one another in one body. As St Ignatius of Antioch (a disciple of the apostle John) said at the end of the first century to the Philadelphians, “Take care, then, to use one Eucharist, so that whatever you do, you do according to God: for there is one flesh of our Lord Jesus Christ, and one cup in the union of his blood; one altar, as there is one bishop with the presbytery.” There is no Christian life without the sharing of the Body and Blood of Christ, the medicine of immortality that nourishes us unto eternal life and unites us to him and to one another in one body.
Fourth, they were devoting themselves to the prayers. It is important to notice that Luke deliberately uses the article here, the prayers. This means that they were devoting themselves to the liturgical, communal prayers, as they had always done in their synagogues and in the temple. They were probably using the liturgical prayers from the Jewish prayer books, which included primarily the Psalms and prayers based on the Psalms and the rest of Scripture – now redefined and fulfilled by Christ himself, the One whom the Church now called upon as the Lord, the God of Israel.
The Church was a praying Church. They prayed individually and extemporaneously, but they also gathered together as the fellowship of the body of Christ to worship liturgically in the preaching of the the apostolic Tradition, the fellowship, the partaking of the Eucharist, and the communal, liturgical prayers.