“And on the seventh day God finished his work that he had done, and he rested on the seventh day from all his work that he had done. So God blessed the seventh day and made it holy, because on it God rested from all his work that he had done in creation.” (Genesis 2:2-3)
On both the Hebrew (a.k.a. Jewish) and the Gregorian calendars, Saturday is the 7th day of the week (Sunday is the 1st day of the week for 55% of the earth’s population). Hence, there is absolutely no justification for keeping Sunday holy on a weekly basis in the scriptures.
“And he said to them, “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)
The Sabbath command is valid for anyone who professes the name of Yeshua Messiah commonly known as Jesus Christ. There is simply no way around it. The Sabbath is mentioned 115 times in the NKJV and not once is it repealed or changed. Christians are adopted into the house of Abraham and, as such, we worship the same God of Abraham, Isaac, Jacob, and Yeshua (Jesus).
“And after these things Paul departed from Athens and came to Corinth. And finding a certain Jew named Aquila, born in Pontus, lately come from Italy with his wife Priscilla (because Claudius had commanded all Jews to depart from Rome) Paul came to them. And because he was of the same trade, he stayed and worked with them; for they were tentmakers by occupation. And he reasoned in the synagogue on every sabbath, persuading both Jews and Greeks.” (Acts 18:1-4)
This is crucial. Paul worked a normal job during the week, then evangelized on the Sabbath, in the synagogue, with the Jews and Greeks. Also, it is very important to note that the book of Acts was written decades after the event described within that book happened. In that light, it is very strange that they never refer to the Sabbath in the past tense, like it was no longer being kept.
The Sabbath will be kept in the millennium to come, after Jesus’ return. If the Sabbath was kept from Adam to Jesus, and it is going to be kept in the future, then why not now?
“And it will be, from one new moon to another, and from one sabbath to another, all flesh will come to worship before Me, says the LORD.” (Isaiah 66:23)
For instructions on how to keep the Sabbath, click Sabbath Keeping Basics – First Century Christianity