Vayakhel

DO NOT KINDLE A FIRE ON THE SHABBOS DAY, IN ANY OF YOUR DWELLING PLACES (Shmos 35:3).

There are 39 melachos, known by Oral Tradition, forbidden on Shabbos.  Why is only igniting a fire listed by the Torah?


Rashi cites one opinion in the Talmud that fire, though strictly forbidden, is a lesser transgression than other types of work.  This is why fire is singled out in the Torah.


Maharal explains Rashi: Fire is like a semi-melacha.  Combustion can occur naturally and spontaneously, without human input. It is not completely representative of man's mastery of nature.  Torah is making a point that fire  too is forbidden on Shabbos, despite its unique character.

Destructive activity is not generally forbidden during Shabbos on a Torah level (Rabbinic law is a different matter). Fire is destructive in nature, but serves a constructive purpose in many activities needed to build the mishkan.  Torah is making a point that fire is forbidden despite its destructive nature (Sforno).

R. Hirsch expands on Sforno: Though fire is destructive, fire is crucial for human creativity.  It gives man the ability to create tools.  Thus fire gives man mastery of nature.  On Shabbos we cease mastering nature to show we acknowledge the earth belongs to G-d. Productive activity must serve His purposes.