Answer: The Hebrew Scriptures make many, many references to honoring the Sabbath, beginning with the injunction to honor it because that is when God rested from creating the world. For hundreds of years Jews did this — resting on the seventh day of the week, what we recognize now as Saturday. Jesus, his family, and his apostles did this in his lifetime, attending the synagogue and refraining from unnecessary work on those days.
Question: If the seventh day is the Sabbath of the Father and is rated among the 10 commandments as equally important, how is it that Sunday has been chosen for worship and the Seventh Day forgotten?
A change happened several decades after Jesus’ death and resurrection because Jesus’ apostles, who were all Jewish and were accustomed to attending synagogue services on Saturdays, were trying to assimilate their new beliefs in Jesus as the Son of God with their developing practice of celebrating the Eucharist. (More accurately these early followers of Jesus after his resurrection are known as Jewish-Christians.)
Eventually it became incompatible for Jewish-Christians to continue worshipping in the synagogue with Jews who didn’t profess Jesus as their savior. The Jewish-Christians then began celebrating the Sabbath on Sundays (the first day of the week) as a testament to the day that Jesus rose from the dead. Over time, Christians have almost all adopted Sunday as their day of weekly worship, the “sabbath” day, with the exception of some like Seventh Day Adventists who still celebrate the sabbath on Saturday.