Sabbath, the seventh day of the week and the Jewish day of rest, derives its beginnings from Genesis. God created the world in six days
and on the seventh day God finished his work which he had done, and he rested on the seventh day from all his work which he had done. So God blessed the seventh day and hallowed it (Gen. 2:2-3)
As practicing Jews, Jesus and his disciples followed the observance of the Sabbath as a day to rest and to gather in worship. Jesus did voice disagreement with some of the rules and regulations and practices that had developed over the years and that were strictly enforced by the Jewish religious hierarchy. "The sabbath was made for man, not man for the sabbath; so the Son of man is lord even of the sabbath." (Mark 2:27-28)
After the death and resurrection of Jesus, early Christian churches adopted various practices. Some churches continued to use the Sabbath, the seventh day of the week, as the day of worship, while others adopted the first day of the week as the proper time for worship in recognition of Christ's resurrection on the first day of the week.
In the year 321, the Roman Emperor Constantine declared Sunday, the first day of the week, to be the officially sanctioned day of rest for citizens of the Roman Empire.
Nowhere. Man changed the Sabbath Day observance to Sunday. Some people claim that the Emperor Constantine changed the observance from Saturday to Sunday.
In the New Testament writings it shows that Paul preached in the synagogues on the Sabbath Day - Saturday. Many religious organizations today, Jewish and Christian adhere to a Saturday (man's term for the day, not God's) Sabbath observance because it is the seventh day of the week.
There are man made observances, teachings, ordinances, laws, and doctrines in various Christian religions, which are not based on the teachings of the Bible. However, me saying that should not be taken as 'gospel'; everyone must prove what is biblical, and what isn't, if this interests them. No one should just rely on what a man says, but should prove all things for themselves.
It is Saturady not Sunday. Man changed it.
@stolperia...so it was man who "changed" the sabbath day to sunday?