The Sabbath is one of the most important commandments in the entire gospel plan

Doctrine and Covenants 59:9

And that thou mayest more fully keep thyself unspotted from the world, thou shalt go to the house of prayer and offer up thy sacraments upon my holy day; https://www.lds.org/scriptures/dc-testament/dc/59?lang=eng

“The Lord declares that to qualify to enter his presence we must live by every word that proceeds forth from his mouth (see D&C 84:44), and the law of the Sabbath is one of the most important in the entire gospel plan.” Mark E. Petersen https://www.lds.org/general-conference/1975/04/the-sabbath-day?lang=eng