The explanation which follows sustains this statement: “The seventh day is the Sabbath [or rest day] of the Lord thy God.”
The origin of this rest day is given in these words: “For in six days the Lord made heaven and earth, the sea and all that in them is, and rested the seventh day: wherefore the Lord blessed the Sabbath day and hallowed it.”
And this is defined to be the day on which he rested from the work of creation.
Moreover the fourth commandment calls the seventh day the Sabbath day at the time when God blessed and hallowed that day, therefore the Sabbath is an institution dating from the foundation of the world."
J.N. Andrews