What are the evidences that the amount of nisab is one-fortieth (1/40) for zakah?

Dear Brother / Sister,

There are statements of the Prophet (pbuh) and the Companions that the amount of nisab is one-fortieth in gold and commercial goods.

The amount of zakah that is fard in gold and silver is 1/40, (one-fortieth) that is two point five percent (2.5 %). When a person has two hundred dirhams and one year passes after obtaining them, he has to give five dirhams as zakah for it. Half a dirham is necessary for twenty mithqals. 

The evidence on which this view is based is the hadiths related to the issue. One of them is the following hadith that the Prophet (pbuh) told Hz. Ali:

"When you possess two hundred dirhams and one year passes on them, you have to pay five dirhams as zakah. Nothing is incumbent on you until it reaches twenty dinars. When you possess twenty dinars and one year passes on them, you have to pay half a dinar as zakah."(1)

The Prophet (pbuh) said,

"There is no zakah for gold that is fewer than twenty mithqals and for silver that is fewer than two hundred dirhams." (2)

"Give one dirham as zakah for every forty dirhams of your money. You do not have to give any money as zakah until it becomes two hundred dirhams. When your money amounts to two hundred dirhams, you have to give five dirhams as zakah. The amount more than that is calculated accordingly for zakah." (3)

Footnotes:

1. Abu Dawud and Bayhaqi narrated this hadith. Naylul-Awtar, IV, 138.
2. Abu Ubayd narrated this hadith.
3. Daraqutni and Asram narrated this hadith. Abu Dawud narrated it from Hz Ali. Hz. Ali narrated it from Ibn Umar.

(Prof. Dr. Wahba Zuhayli, İslam Fıkhı Ansiklopedisi)

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