The sign of obedience is the observance of the Sabbath of the fourth commandment. If men keep the fourth commandment, they will keep all the rest. It was no human voice that spoke to Moses, giving him the Sabbath as a sign. “The Lord spake unto Moses, saying, Speak thou also unto the children of Israel, saying, Verily My Sabbaths ye shall keep: for it is a sign between Me and you throughout your generations; that ye may know that I am the Lord that doth sanctify you. Ye shall keep the Sabbath therefore; for it is holy unto you: everyone that defileth it shall surely be put to death: for whosoever doeth any work therein, that soul shall be cut off from among his people.” TM 134.2
The Lord does not leave so important a precept as this without definite specification. “Six days may work be done; but in the seventh is the Sabbath of rest, holy to the Lord: whosoever doeth any work in the Sabbath day, he shall surely be put to death. Wherefore the children of Israel shall keep the Sabbath, to observe the Sabbath throughout their generations, for a perpetual covenant.” TM 135.1