Rates of Zakah are Specified by Allah
وَالَّذِينَ فِي أَمْوَالِهِمْ حَقٌّ مَّعْلُومٌ (and those in whose riches there is a specified right...Al-Ma'arij 70:24 ⧉). This verse shows that the quantifications of Zakah have been fixed by Allah. The details are recorded in authentic ahadith. These quantifications, whether relating to the nisab (the minimum limit on which Zakah is payable) or to the rate of payment, being fixed by Allah Ta` ala cannot be changed by anyone at any time.