Is the sabbath a covenant with Jews or is sabbath of the Lord ,Adam and Eve kept sabbath?

I am told the reason we do not keep the sabbath any more is because it was a covenant with the Jews and does not apply to us and that Jesus is the new covenant. I also read in Isaiah 56 about the sabbath being for us , it says any one who will receive the Lords blessings.56:4 For thus saith the Lord unto the eunuch that keep my sabbaths, and choose the things that please me, and take hold of my covenant; 56:5 Even unto them will I give in mine house and within my walls a place and a name better than of sons and of daughters: I will give them an everlasting name, that shall not be cut off.56:6 also the sons of stranger, that join themselves to the Lord, to serve him , and to love the name of the LOrd, to be his servants, every one that keepeth the sabbath from polluting it , and taketh hold of my coventant: 56:7 Even them will I bring to my holy mountain, and make them joyful in my house of prayer: their burnt offerings and their sacfifices shall be accepted upon mine