Charles Ellicott Commentary Exodus 31:14

"Ye shall keep the sabbath therefore; for it is holy unto you: every one that profaneth it shall surely be put to death; for whosoever doeth any work therein, that soul shall be cut off from among his people." — Exodus 31:14 (ASV)

Every one that defileth it shall surely be put to death. —This is a new enactment and must be regarded in conjunction with the new dignity attached to Sabbath observance because it had become the special covenant sign between God and His people. The Sabbath-breaker now threw himself out of covenant with God, and not only that, but did what he could to throw the whole people out of covenant. His guilt was therefore great, and the assignment of the death penalty to it is in no way surprising; rather, it is in accordance with the general spirit of the code (Exodus 21:29; Exodus 22:18–20, and others). When the occasion arose, there was no hesitation in carrying out the law (Numbers 15:32–35).

Cut off.—Or, separated, set apart from. His act immediately cast him out from among God’s people, made him an outlaw, ipso facto excommunicated him.