Does Zakat become obligatory upon my mother on the money she earns from selling rubber if it is spent on household expenses and nothing is left over?

Jurists have differed regarding what produce from the earth is subject to Zakat. The preponderant opinion is that it is obligatory on everything that is measurable by volume and storable. Rubber is not a staple food.

The Malikis and Shafi'is are of the view that Zakat is not obligatory on rubber because it is not a staple food. However, Zakat becomes obligatory on its price if it reaches the nisab (threshold) and a hawl (full lunar year) passes over it.

As for the Hanbalis, Zakat is not obligatory on rubber according to them, because it is not stored dry, similar to vegetables and olives.

The Fatwa Committee of the Kuwaiti Ministry of Awqaf has adopted this view, and has decided that Zakat is not obligatory on rubber.