By the end of the first century, Christians had developed a clearly defined way of worshiping. The Church was growing fast and was becoming increasingly involved with the world beyond its Jewish roots. As it did so, it had to grapple with a stream of theoretical and practical questions.

The early Christians‟ pattern of worship was very similar to that of their successors today. They met on Sunday, the day of the Resurrection, rather than Saturday, the Jewish Sabbath. When they met they celebrated the Eucharist, studied the Scriptures, prayed, and sang hymns together. Buildings created specifically for Christian worship did not appear until Christianity became officially tolerated in 313, and so, having no other choice, the early Christians met in one another‟s houses. As time went by, some large houses were specially modified to accommodate church meetings.

Groups generally met very early in the morning. They read from the Jewish prophets as well as from the writings of the Apostles and evangelists. The leader of the liturgy commented on the texts that had been read, and those present may have added their own thoughts and observations. Prayers were also offered for people in need and on behalf of the sick, and Pliny tells us that they “sang a hymn to Christ as God.”

Writing in the 150s, Justin Martyr gives us some idea of how the Christians gathered for worship: “On the day called after the sun there takes place a meeting of all who live in towns or in the country. The memoirs of the apostles are read, as are the writings of the prophets, insofar as time will allow. When the reader has finished, the president, in his speech, admonishes and urges all to imitate these worthy examples. Then we all stand and pray together aloud. When the prayers are ended, we greet one another with a kiss. At that point, as we have already said, bread is brought, with wine mixed with water to the president,” who accepted them and prayed, offering up “praise and glory to the Father of the Universe, through the name of the Son and the Holy Spirit,” and then giving thanks “for our being deemed worthy to receive these things at his hands.” When he had concluded the prayers and thanksgivings, “the people consent by saying Amen – so be it.”

The bread and wine over which the thanksgiving had been said were then distributed by deacons, who later brought the bread and wine to those who could not be at the meeting. Justin said that participation in the Eucharist was limited: “None is allowed to share unless he believes the things which we teach are true, and has been washed with the waters that bring the remission of sins and give a second birth, and lives as Christ ordered us so to live. For we do not receive them as ordinary bread and ordinary wine, but as Jesus Christ our Savior.”

The form of liturgy Justin describes, centered on Bible reading, sermon, prayers, and communion, has often been elaborated on but in outline it has remained unchanged, the basic pattern of worship for most Christians for 2,000 years.

Every Sunday the fast-growing congregations needed to be taught. There were many different interpretations of the Scriptures, and, if Christians were not to be led astray, false teachers had to be rebuked, discipline maintained, and complicated questions of theology resolved. Was Jesus in fact God, in human disguise, or was he truly both God and man? Which pagan customs were acceptable for Christians, and which must be rejected? Could Christians who grievously sinned be forgiven and restored to full fellowship?

Searching the Scriptures for answers to these questions, different teachers disagreed. It fell to the bishops to decide on the basis of Scripture and of the oral tradition passed down to them from the Apostles; both were equally valued. As Papias (c.60–130), bishop of Hierapolis in Asia Minor, put it, “I shall not hesitate to set before you, along with my own interpretation, everything I carefully learned from the elders and care-fully remembered … It seemed to me that I could profit more from the living voice than from books.”

The most famous post-apostolic leaders became known as the Apostolic Fathers for their proximity to the era of the Apostles and their fidelity to the doctrine of the Apostles. The earliest is Clement, perhaps the third or fourth successor of Peter as bishop of Rome. Writing in c.85 to the same community at Corinth to which Paul had once addressed his letters, Clement reproved a number of Christians: “You will please us greatly if, being obedient to the things which we have written through the Holy Spirit, you will root out the wicked passion of jealousy, in accord with our call for peace and concord.” Other Apostolic Fathers included Bishop Polycarp of Smyrna, and Papias, who wrote the five-volume Expositions of the Sayings of the Lord, of which only fragments remain. Figures such as these provide a human link back to the Apostles, whom they knew – Polycarp claims that the boy who offered Jesus loaves and fish to perform a miracle later became bishop of Tours, in France.

Ignatius, bishop of Antioch in Syria, was another highly influential figure. He is known through the seven letters he wrote on the way to his martyrdom at Rome in c.107, in which he defended the Incarnation, insisting that Christ is both divine and human, “both flesh and spirit, born and unborn, God in man, true life in death, … first subject to suffering and then beyond it.” He also taught that the bishops guard the unity of the faith, so that “we ought to regard the bishop as the Lord himself.” As he went to be martyred, he wrote, “It is better to die for Jesus Christ than to rule over the ends of the earth.

Ignatius had an exalted view of communion, writing of it as breaking “one bread … the medicine of immortality.” This view was shared by the unknown author of the Didache, or The Teaching of the Twelve Apostles, which decreed: “On the Lord‟s own day gather together and break bread and give thanks, having first confessed your sins so that your sacrifice may be pure.” Indeed, the Apostolic Fathers were as one in their view of the Church and its worship: one united body, focused on baptism, communion, prayer, and study of the Scriptures, under the rule of bishops.