The Sabbath refers to Saturday, which the Old Testament calls "the day of rest," in commemoration of the six days God took to create the world. The first reference to the Sabbath is, therefore, in Genesis 2:2, the first book of the Hebrew Scriptures. An explicit call to keep the Sabbath as a day of rest can be found in Exodus 31:14, where believers are called to always observe the Sabbath, or else face the wrath of God. In addition to the Hebrew Scriptures, the Gospels of Mark, Matthew, Luke and John make reference to the Sabbath 51 times and for Jews, this has been interpreted to be on Saturday for thousands of years.
It was, in fact, the early Catholic Church that decided to change the day of the Sabbath from Saturday to Sunday and the majority of Protestant denominations have not contested this change. This dates back to the earliest days of the Church, when Christians held their weekly gatherings on Sunday, rather than on Saturday, which the Jews continued to observe as the Sabbath.
It was, in fact, the early Catholic Church that decided to change the day of the Sabbath from Saturday to Sunday and the majority of Protestant denominations have not contested this change. This dates back to the earliest days of the Church, when Christians held their weekly gatherings on Sunday, rather than on Saturday, which the Jews continued to observe as the Sabbath.
