"Thus the heavens and the earth were finished, and all the host of them. And on the seventh day God ended his work which he had made. And God blessed the seventh day, and sanctified it: because, that in it, He had rested from all his work which God created and made." (Gen 2:1-3).The bible reveals that God blessed and set apart (sanctified) the seventh day.
This day is holy unto God, and it is the only day of the week that we are commanded to honor.
"Six days shall work be done: but the seventh day is the Sabbath of rest, an holy convocation: ye shall do no work therein: it is the Sabbath of the Lord in all your dwellings." (Lev 23:3).
A holy convocation is an assembly of the people of God, who come together to worship him.