The "First Day of the Week" holds significant importance in Christian tradition and is commonly understood as Sunday. This day is recognized as the day of Jesus Christ's resurrection, which is a cornerstone event in Christian theology. The resurrection is celebrated by Christians as a symbol of new life and hope, marking the triumph over sin and death.

Biblical References:

1. Resurrection of Jesus:
The Gospels record that Jesus rose from the dead on the first day of the week. In Matthew 28:1 , it states, "After the Sabbath, at dawn on the first day of the week, Mary Magdalene and the other Mary went to see the tomb." Similarly, Mark 16:2 notes, "Very early on the first day of the week, just after sunrise, they went to the tomb." These accounts emphasize the significance of the first day as the time of the resurrection.

2. Appearances of the Risen Christ:
Jesus appeared to His disciples on the first day of the week. In John 20:19 , it is written, "It was the first day of the week, and that evening, while the disciples were together with the doors locked for fear of the Jews, Jesus came and stood among them. 'Peace be with you,' He said to them." This appearance underscores the importance of the first day as a time of revelation and fellowship with the risen Lord.

3. Early Christian Worship:
The early church adopted the first day of the week as a time for gathering and worship. Acts 20:7 records, "On the first day of the week, we came together to break bread. Paul spoke to the people and, because he intended to leave the next day, kept on talking until midnight." This passage indicates that the early Christians gathered on this day for communal worship and teaching.

4. Collection for the Saints:
The Apostle Paul instructed the Corinthian church to set aside a collection on the first day of the week. In 1 Corinthians 16:2 , he writes, "On the first day of every week, each of you should set aside a portion of his income, saving it up, so that when I come no collections will be needed." This practice reflects the organizational and communal aspects of early Christian life.

Theological Significance:

The first day of the week, Sunday, became known as the "Lord's Day" in Christian tradition, a term that appears in Revelation 1:10 , where John writes, "On the Lord’s day I was in the Spirit, and I heard behind me a loud voice like a trumpet." This designation highlights the day's special status as a time for worship and reflection on the resurrection of Christ.

The shift from the Jewish Sabbath (Saturday) to Sunday worship reflects the new covenant established through Jesus' death and resurrection. It symbolizes the new creation and the fulfillment of the Old Testament promises. The observance of Sunday as a day of worship and rest is seen as a celebration of the new life and eternal rest found in Christ.

Historical Context:

Historically, the first day of the week became the primary day of Christian worship by the second century. Early church fathers, such as Ignatius of Antioch and Justin Martyr, wrote about the practice of gathering on Sunday to commemorate the resurrection. This tradition has continued throughout Christian history, with Sunday services being central to Christian communal life.

In summary, the first day of the week is deeply embedded in Christian theology and practice as the day of Christ's resurrection, a time for worship, and a symbol of the new covenant. It serves as a weekly reminder of the hope and victory found in Jesus Christ.