“Awake, O sleeper,
and arise from the dead,
and Christ will give you light.”
These are the words spoken by Saint Paul which many say might have been part of an early Christian hymn especially for the baptismal liturgy. Every Holy Saturday the Church throughout the world celebrates the day Christ rested in the tomb and we awaited the day of His Resurrection. Due to the antiquity of this celebration along with us Catholics, the Eastern Orthodox, the Oriental Orthodox, the Anglicans and the Lutherans all celebrate this festivity.
In the creation story we see God created the world in six days and on the seventh day He rested from His works. Because of this God consecrated the seventh day, the Sabbath, as a day of rest for the Israelites (rf. Exodus 20:8-11). However we see a shift from Saturday to Sunday as the day of rest and worship; for “on the first day of the week” Christians assembled (rf. Acts 20:7) and collected the offerings for the Church (rf. 1 Corinthians 16:2) since it was on this day Jesus Christ rose from the grave (rf. Matthew 28:1, Mark 16:2, Luke 24:1, John 20:1). Sunday celebrates the new creation for this reason. Saint Justin Martyr mentions on Sunday all Christians living “in cities or in the country gather together to one place” to read the Scriptures, that “all rise together and pray”, then “bread and wine and water are brought, and the president in like manner offers prayers and thanksgivings” and these bread and wine “by transmutation are nourished” to become “the flesh and blood of that Jesus who was made flesh” (cf. First Apology 66-67). Here we see the early liturgy of the Church, with a basic framework as it does today: there is the Liturgy of the Word (the reading of Scriptures), the Liturgy of the Eucharist, the sign of peace and standing for prayer. Details of the liturgy might have change according to time and place, but these basics are there already in the first two centuries of the Church.
The passage of Ephesians 5:14 both relates to Holy Saturday, asking for Jesus to arise, and to Baptism in which the candidate arises with Jesus and is given His light. Saint Paul mentions the significance of Baptism in very sacramental language, saying we “who are baptized in Christ Jesus, are baptized in his death” (cf. Romans 6:3) and that we are risen with Him (v. 4). It is fitting for this reason that as an ancient custom the Church generally baptizes people during the Easter season.
Statue of Jesus lying in the tomb, Monastery of Saints Joachim and Anna, Valladolid, Spain