The Lord  said  "... The Sabbath was made for man, and not man for the Sabbath." See Mark 2:27.  But, it is still the Sabbath and the only day on which the Lord would have ceremonial rest while also working in service. The Lord worshiped on the Sabbath. The Apostles shared the message of salvation first and foremost, relaxing the Jewish Sabbath custom to ensure that the message of salvation was communicated. The message is salvation and grace in the law and also a message of relationship so that the relationship and experience of Abraham as taught by Christ would be shared with the children of Abraham and also the Gentiles. As such, relationship precedes a life by the law. But, the law remains and is maintained with the understanding that following the law in its entirety without sincere relationship will not amount to anything but a dead, formulaic religion and not relationship. There has to be sincere relationship to accompany respect for the law and also the Sabbath. If someone chooses to worship on the Sabbath and has become convinced that this is his or her day of worship, let them be at peace and convinced but those who worship on some other day can recognize that the Sabbath will always be the Sabbath.  The Sabbath will not change and in either case, let those who recognize Christ as their savior remain in sincere relationship. See 1st John 1.