The only day that does not fit into the pattern is day seven. This emphasizes the seventh day and sets it apart from the first six days. God blesses the seventh day and commands that it be kept holy. Jewish people had a sense of pride because of this beautiful tradition; they practiced it and passed it on to their children. The Israelites were the only people who practiced the custom of resting on the seventh day in the ancient world. God prescribed the ritual of setting aside the seventh day and keeping it holy to his chosen people, the people he set aside.
Why is the Sabbath on the first day for Christians? Christians continued the tradition of rest on the Sabbath, but the Sabbath for the Christian is on the first day of the week, rather than the seventh. The Third Commandment, says “Remember to keep holy the Lord’s day” and the first of the five precepts of the Church, “You shall attend Mass on Sundays and on holy days of obligation and remain free from work or activity that could impede the sanctification of such days.” [2] The evangelists Matthew, Mark, Luke, and John all stress that Jesus rose on the first day of the week. It was important for the early Christians who rested and worshiped on Sunday, to identify and distinguish themselves from the Jewish tradition of resting and worshipping on Saturday. It was on Sunday, the first day, the Jesus makes all things new. This is the new creation in which Jesus who slept in death, now rises. “I slept on the cross and a sword pierced my side for you who slept in paradise and brought forth Eve from your side. My side has healed the pain in yours. My sleep will rouse you from your sleep in hell.”
[iii] Jesus is the meek and humble lamb led to the slaughter on Good Friday, sleeps on Saturday, but on Sunday, He is the Lion of Judah, whom awakened by His Father’s voice, rises from sleep.
[1] Fr. John A. Hardon, S.J., Modern Catholic Dictionary, pg. 476
[2] Compendium: Catechism of the Catholic Church; Appendix B: Formulas of Catholic Doctrine; page 193