An interesting thing about the Sabbath law is that it is the only one of the ten commandments
that is not repeated anywhere in the new testament. This is the why many christians do not "keep the sabbath holy"
"and the Sabbath of most Christians on Sunday"
This isn't exactly true (though I suppose no statement about christians is totally true.) Most christians still call Saturday the sabbath, but they are not inclined to observe it. Most (in protestant circles at least) call sunday 'the lord's day.' This is done because Jesus was risen from the dead on a Sunday, because Pentecost occured on a Sunday, and because the church of Acts met on Sunday.
ha, the dictionary bot isn't as smart as he looks.