The consecration of Sunday has been a Church Tradition, observed by the Apostles who took it from the teaching of the Lord Jesus Christ; it is not mentioned plainly in the Gospels but there are references in the Book of Acts that imply this Divine entrustment. So the matter changed to a professed practice of the Church without the need for a written commandment. A proof of acknowledging Tradition is the unanimity of all Churches in keeping Sunday holy.