Quite a responce
In its inception the church which Jesus built came out of a Jewish culture, it is really hard to tell how long, but throughout most of the book of Acts Jews predominated over Gentiles in membership. The fact that the apostles refer to Moses and Abraham among others spoken of in the Old(er) Testament indicates that the early church, the ekklasia of Messiah, was Jewish in its "roots". Indeed the gospel was first to the Jews and then to the Greeks.
Much of what is carried along by Christians regarding the Sabbath is tradition and nothing more. The truth of this is to be found in Scripture; Acts 15:
22 Then it pleased the apostles and elders, with the whole church, to send chosen men of their own company to Antioch with Paul and Barnabas, namely, Judas who was also named Barsabas,[e] and Silas, leading men among the brethren.
23 They wrote this, letter by them:
The apostles, the elders, and the brethren,
To the brethren who are of the Gentiles in Antioch, Syria, and Cilicia:
Greetings.
24 Since we have heard that some who went out from us have troubled you with words, unsettling your souls, saying, You must be circumcised and keep the law[f]to whom we gave no such commandment 25 it seemed good to us, being assembled with one accord, to send chosen men to you with our beloved Barnabas and Paul, 26 men who have risked their lives for the name of our Lord Jesus Christ. 27 We have therefore sent Judas and Silas, who will also report the same things by word of mouth. 28 For it seemed good to the Holy Spirit, and to us, to lay upon you no greater burden than these necessary things: 29 that you abstain from things offered to idols, from blood, from things strangled, and from sexual immorality.[g] If you keep yourselves from these, you will do well.
Farewell.
These were the commands of the Apostalic council, if Christians were to keep the Sabbath, it would have been listed here.
But I still contend that those who think they are keeping the Sabbath today are not really doing so. The command regarding the Sabbath is clear and those who were to keep it were clear on who they were.