The Octave of Easter refers both to the first eight days of Easter and to the eighth day in particular. So, the Sunday after Easter Sunday is the Octave of Easter. 'Eight' is a significant number in Christian symbolism and is related to why Sunday is the main day of worship for Christians.
But on the first day of the week, at early dawn, they came to the tomb, taking the spices that they had prepared. They found the stone rolled away from the tomb, but when they went in, they did not find the body.
– Luke 24:1-3
In the Acts of the Apostles, we are told that Paul preached "on the first day of the week when we had gathered to break bread." - Acts 20:7
On the Lord’s day, gather together and break bread and give thanks.
– Didache 14:1 (c. 100 A.D.)
Sunday is the day on which we hold our common assembly, for this is the first day on which . . . Jesus Christ our Savior . . . rose from the dead.
– Justin Martyr, The First Apology, Chapter LXVII (2nd century)
Because it is the day of Jesus’ resurrection and victory over sin and death, Sunday became known as “the Lord’s day” and eventually became the chief day of Christian celebration and worship. Every Sunday is therefore a commemoration of Easter.
But worshiping on Sunday is not just about looking back with gratitude for an event in the past. Because it is the day of resurrection, Sunday became understood as not just the first day of the week, but also as the first day of the New Creation. As such, Sunday came to be referred to as the “eight day”. In an early Christian text that was not included in the Bible, we read,
. . . when giving rest to all things, I shall make a beginning of the eight day, that is, a beginning of another world. Wherefore, also, we keep the eighth day with joyfulness, the day also on which Jesus rose again from the dead.
– Epistle of Barnabas, 15:8 (c. 100 A.D.)
Thus, worship on Sunday is a present invitation to enter into the new creation in Christ (cf. 2 Corinthians 5:17).
But, worshiping on Sunday is also a reminder that the church is called to live in expectation of the new creation promised by God and inaugurated by Jesus.
For I am about to create new heavens and a new earth; the former things shall not be remembered or come to mind. But be glad and rejoice forever in what I am creating; for I am about to create Jerusalem as a joy, and its people as a delight. I will rejoice in Jerusalem, and delight in my people; no more shall the sound of weeping be heard in it, or the cry of distress. . . . They shall not labor in vain, or bear children for calamity; for they shall be offspring blessed by the Lord— and their descendants as well. Before they call I will answer, while they are yet speaking I will hear. The wolf and the lamb shall feed together, the lion shall eat straw like the ox; but the serpent—its food shall be dust! They shall not hurt or destroy on all my holy mountain, says the Lord.
– Isaiah 65:17-19, 22-25 (cf. Revelation 21:1-5)
As “eighth day people”, Christians are called to bear witness to, and shape our lives now in anticipation of, the fulfillment of that new creation.
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