He made it holy for special use. God did not bless the ACT of resting, He blessed a specific DAY . If the whole world rested on some day it wouldn't make that day a Sabbath. What makes it the Sabbath is that God rested, blessed and made it holy. People do not have the authority to change what God has sanctified.
Some people feel it makes no difference what day is kept as long as they keep one day in seven.
This point is very clear in Scripture. The Sabbath is a creation rememberence, coming to us from the Garden of Eden before Adam and Eve sinned. On the cross Jesus dealt with sin. Since the Sabbath existed before sin, there is absolutely no way it could be altered by the cross. The Sabbath existed thousands of years before there was a Jew.