What is the established Nisab for gold?
Chapter on Zakat on Gold and Silver
Al-Mughni
Book of Zakat
Primary text
The established Nisab for gold is twenty Mithqals, without consideration of its equivalent value in silver, which is the position of the majority of jurists. This is supported by the Hadith narrated by Amr ibn Shu'ayb, from his father, from his grandfather, that the Prophet (PBUH) said, "There is no charity on less than twenty Mithqals of gold, nor on less than two hundred Dirhams" (Narrated by Abu Ubayd). Ibn Majah narrated from Ibn Umar and Aisha that the Prophet (PBUH) used to take half a Mithqal for every twenty Dinars and more, and a full Mithqal for forty Dinars. Since gold is wealth on which Zakat is due on its substance (ayn), it should not be measured against another asset, similar to other zakatable properties.
Supporting text
A differing view is attributed to 'Ata', Tawus, Al-Zuhri, Sulayman ibn Harb, and Ayyub Al-Sakhtiyani, who stated that the gold Nisab is contingent upon the silver standard, meaning Zakat is due only when the value of the gold reaches two hundred Dirhams, due to the lack of a specific measure for gold from the Prophet (PBUH). Consensus exists that if gold is less than twenty Mithqals but does not reach the value of two hundred Dirhams, no Zakat is due, except what is related from Al-Hasan who suggested Zakat is due only upon reaching forty Dinars.