One of the Ten Commandments states: "Remember the Sabbath day, to keep it holy. Six days you shall labor and do all your work, but the seventh day is the Sabbath of the Lord your God. In it you shall do no work" (Exodus 20:8-10 Exodus 20:8-10  Remember the sabbath day, to keep it holy.
 Six days shall you labor, and do all your work:
 But the seventh day is the sabbath of the LORD your God: in it you shall not do any work, you, nor your son, nor your daughter, your manservant, nor your maidservant, nor your cattle, nor your stranger that is within your gates:
American King James Version×).
There is no biblical authority for changing the day of rest and worship from the seventh-day Sabbath to Sunday.
God commanded that the seventh day be observed as the Sabbath. A glance at almost any dictionary or encyclopedia will show you that Saturday is the seventh day of the week, while Sunday is the first day of the week. The seventh day according to God's calendar is—and always has been—the Sabbath day. Although man has modified calendars through the centuries, the seven-day weekly cycle has remained intact throughout history. The days of the week have always remained in their proper order, with Sunday as the first day of the week and Saturday as the seventh.
"The oracles of God"—His divine words and instructions recorded in the Holy Scriptures including the Commandments—were entrusted to the Jewish people (Romans 3:1-2 Romans 3:1-2  What advantage then has the Jew? or what profit is there of circumcision?
 Much every way: chiefly, because that to them were committed the oracles of God.
American King James Version×), and they have preserved the knowledge of the seventh-day Sabbath faithfully since well before Christ's time to this day.
No biblical authorization to change the Sabbath to Sunday
How did Sunday become the primary day of rest and worship? Although the concept of rest has largely disappeared, most churches continue to hold their worship services on Sunday. You can search throughout the Bible, but you will find no authority to alter the day of worship.
James Cardinal Gibbons, Catholic educator and archbishop of Baltimore in the late 1800s and early 1900s, was blunt about the change:
"You may read the Bible from Genesis to Revelation, and you will not find a single line authorizing the sanctification of Sunday. The Scriptures enforce the religious observance of Saturday, a day which we never sanctify. The Catholic Church correctly teaches that our Lord and His Apostles inculcated certain important duties of religion which are not recorded by the inspired writers...We must, therefore, conclude that the Scriptures alone cannot be a sufficient guide and rule of faith" (The Faith of Our Fathers, 1917, p. 89).
Did you catch that? The writer admits that Sunday observance is nowhere authorized in the Bible and that the seventh day is the only day sanctified by the Scriptures. His justification for changing the day of rest and worship assumes that authority exists apart from the Bible to define the necessary truths and practices for salvation.
Sabbath change made after the New Testament was written
The change from Sabbath to Sunday was made long after the writing of the New Testament. No clear references to Sunday as a day of Christian worship are found until the writings of Barnabas and Justin, c. A.D. 135 and 150, respectively. Observance of Sunday as the primary day of worship appears to have solidified in the reign of Emperor Hadrian (A.D. 117-135), who harshly persecuted Jews throughout the Roman Empire. Hadrian specifically prohibited practices of Judaism, including observance of the seventh-day Sabbath.
These oppressive measures apparently influenced many early Christians in Rome to abandon the seventh day and turn to Sunday, historically observed by the Romans as a day of veneration of the sun (hence the name of the day). Within a few centuries Sabbath observance by Christians was virtually eliminated within the confines of the empire and replaced by Sunday.
Although the Protestant Reformation brought some doctrinal and administrative changes, observance of Sunday as a day of rest and worship continued from the Roman Catholic Church into subsequent Protestant denominations. Whereas the Catholic Church claimed authority to establish its own times of worship, Protestant churches generally justified Sunday observance on the grounds that the seventh-day Sabbath was replaced in the New Testament by worship on Sunday in honor of Christ's resurrection.
As confirmed by Cardinal Gibbons above, there is no biblical authority for changing the day of rest and worship from the seventh-day Sabbath to Sunday. As shown in our free booklet Sunset to Sunset: Gods Sabbath Rest, Jesus Christ, the apostles and Jewish and gentile members of the early Church alike continued to observe the Commandments, including the seventh-day Sabbath. This is the only day authorized in the Bible.
How do Christians observe God's Sabbath days?
The weekly Sabbath is also a holy time to God. It's a day of rest, and Christians honor God by following His example of resting on the seventh day (Genesis 2:2 Genesis 2:2And on the seventh day God ended his work which he had made; and he rested on the seventh day from all his work which he had made.
American King James Version×). Part of resting is not doing any of our usual work on the Sabbath, as well as on the biblical festivals as instructed in Leviticus 23.
The Sabbath days are times of a “holy convocation,” which is a “sacred assembly” (Leviticus 23:4 Leviticus 23:4These are the feasts of the LORD, even holy convocations, which you shall proclaim in their seasons.
American King James Version×, New International Version) that God has commanded. Today we conduct services that include sermons and congregational hymns, preceded and followed by Christian fellowship.