Taking on the view of someone following God, God said when creating the earth to work 6 days and to keep the 7th holy. He even says in the 10 commandments to keep the Sabbath holy (which Is the 4th commandment). So not keeping the Sabbath was basically disobeying God which is why its so important for followers of Judaism (and Judea-Christians) to keep it holy/a day of rest.
