Sacraments
Early Christian Worship
The liturgy of the first three centuries, as attested by writers like Justin Martyr and the Didache, already contains the recognizable structure of the Catholic Mass: Scripture readings, a homily, intercessions, and the Eucharistic sacrifice.
Catholic teaching
The Church teaches that the liturgy she celebrates today is the same essential act of worship handed down from the apostles, developed organically in its rites and prayers but continuous in substance: the gathering of the faithful on the Lord's Day to hear the word of God, offer the Eucharistic sacrifice, and receive Holy Communion. This continuity is a mark of authenticity, distinguishing the Catholic and Orthodox liturgical traditions, rooted in apostolic practice, from worship forms invented centuries later that lack this historical lineage.
Biblical foundation
Acts describes the first Christians as devoted to the apostles' teaching, to fellowship, to the breaking of the bread, and to the prayers, a fourfold pattern of Scripture, community, Eucharist, and liturgical prayer. Paul's instructions to the Corinthians about how to conduct themselves 'when you come together' presuppose an already-structured communal liturgy with distinct roles. The Book of Revelation's heavenly worship scenes, with an altar, incense, elders, and the slain Lamb, deeply influenced the shape of the early Church's earthly liturgy.
Scripture references
Historical evidence
St. Justin Martyr's First Apology, written around AD 155 to the Roman emperor, gives a detailed eyewitness description of the Sunday liturgy in Rome: readings from 'the memoirs of the apostles' and the prophets, a homily by the president, common prayers, the kiss of peace, the offering of bread and wine mixed with water, a Eucharistic prayer, the people's 'Amen,' and distribution of the consecrated elements even to the absent by deacons—a structure immediately recognizable as the ancestor of the Mass. The Didache, dated even earlier, contains Eucharistic prayers and instructions to confess sins before offering the sacrifice 'that your sacrifice may be pure.'
The Church Fathers
“On the day called Sunday, all who live in cities or in the country gather together to one place, and the memoirs of the apostles or the writings of the prophets are read.”
“We give thee thanks, Holy Father, for thy holy name which thou didst cause to tabernacle in our hearts.”