A slave does not enjoy rest. A son does. If God created the Sabbath for mankind, why not enjoy it?
In terms of history, culture, and covenants, the Gospel was promised and preached to the Jews first, then to the Gentiles.
Messianic Judaism is a Biblically based movement of people who, as committed Jews, believe in Yeshua (Jesus) as the Jewish Messiah of Israel of whom the Jewish Law and Prophets spoke. (MJAA.org)