Chapter I: Importance of the Liturgy of the Hours or Divine Office in the Life of the Church
1. Public and common prayer by the people of God is rightly considered to be among the primary duties of the Church. From the very beginning those who were baptized "devoted themselves to the teaching of the apostles and to the community, to the breaking of the bread, and to prayer" (Acts 2:42). The Acts of the Apostles give frequent testimony to the fact that the Christian community prayed with one accord. 
The witness of the early Church teaches us that individual Christians devoted themselves to prayer at fixed times. Then, in different places, it soon became the established practice to assign special times for common prayer, for example, the last hour of the day when evening draws on and the lamp is lighted, or the first hour when night draws to a close with the rising of the sun.
In the course of time other hours came to be sanctified by prayer in common. These were seen by the Fathers as foreshadowed in the Acts of the Apostles. There we read of the disciples gathered together at the third hour.  The prince of the apostles "went up on the housetop to pray, about the sixth hour" (10:9); "Peter and John were going up to the temple at the hour of prayer, the ninth hour" (3:1); "about midnight Paul and Silas were praying and singing hymns to God" (16:25).
2. Such prayer in common gradually took the form of a set cycle of hours. This liturgy of the hours or divine office, enriched by readings, is principally a prayer of praise and petition. Indeed, it is the prayer of the Church with Christ and to Christ.