Numbers 15:35 - Joseph Benson’s Commentary on the Old and New Testaments

The man shall surely be put to death One reason why the breach of the sabbath was punished with such severity by the Jewish law is, that it was an implicit denying of God to be the Creator of the world. For the sabbath being a sign, (Exodus 31:13,) whereby the worshippers of the one true God, who created the world, were distinguished from the idolatrous nations, who believed the world was eternal, and who worshipped the sun, moon, and stars, and a multitude of nominal gods, the violation of this institution implied or led to a defection from the true religion to polytheism and idolatry.