Why Zakah is payable at a rate of 2,5% on most types of wealth
7-12-2009 | IslamWeb
Question:
Assalamulaikum, Dear Sir, one of my friend has very shame full misconceptoon about paying zakat.his question is about references of 2.5% percentage on income and other assets from quran and hadith.(that 2.5% zakat is specifically obligatory) and second question about zakat on the land(as an asset) which is not uder use.so one has to pay zakat on that. please give references from quran and hadith. jazakallajh khair. mnay thanks.
Answer:
All perfect praise be to Allaah, The Lord of the Worlds. I testify that there is none worthy of worship except Allaah, and that Muhammad 
is His slave and Messenger.
First of all, it should be mentioned that it is not an obligation to pay Zakah on everything that a person possesses, rather, Zakah is obligatory only on particular types of wealth, and its amount is not only 2,5 %, but it differs according to the type of wealth on which Zakah must be paid and the manner of the growth of such type of wealth.
Moreover, you should know that Zakah on gold and silver and other currency notes that are like gold and silver and tradable items is 2,5 %. The evidence about this is the Sunnah and the consensus of the scholars 
. The evidence from the Sunnah is that many Ahaadeeth were reported in this regard like the saying of the Prophet said: “Sadaqah on silver is a fourth of a tenth (i.e. 2,5%).’’ [Maalik, Al-Bukhari, An-Nasaa’i and Ibn Maajah] Besides, Ali 
narrated that the Prophet said: ''If you possess 200 (silver) Dirhams and a whole lunar year elapses on it, then 5 Dirhams must be paid out on it, and you are not obliged to pay Zakah unless you possess 20 (gold) Dinars and a whole lunar year elapses on it, in which case, you should pay half a Dinar and any additional amount should be based on this, and Zakah on money is only due if a whole lunar year elapses on it.’’ [Abu Daawood]
In addition, Ibn ‘Umar and Aa’ishah 
narrated that the Prophet used to take on every 20 Dinars half a Dinar, and one Dinar on 40 Dinars and so forth…[Ibn Maajah]
As regards the consensus of the scholars then Ibn Qudaamah 
said: “We do not know any difference of opinion among the scholars concerning that Zakah on gold and silver is at a rate of 2,5%...” This is also the view of the contemporary scholars, and this is what is established in Islamic Fiqh Committees that the banknotes that is circulated between people are treated exactly like gold and silver in regard to its religious ruling because it represents money in the same way gold and silver were money at the time of the Prophet so it is an obligation to pay Zakah on it [banknotes] if it reaches the Nisaab (minimum amount liable for Zakah).
As regards your question about why the percentage of Zakah is exactly 2,5%, then a Muslim should in principle submit himself to the rulings of Islam whether or not he knows the wisdom thereof. So, it is not correct to ask why Thuhr prayer is 4 Rak’ahs and not 5 Rak’ahs or 3 Rak’ahs, and why Tawaaf is 7 rounds and not 8 rounds or 6 rounds, and so on…That is because such questioning is considered as extravagancy. It is for this reason that when ‘Aa’ishah 
was asked by a woman: ‘‘Why is it that a menstruating woman makes up for her fasting but she does not make up for her prayers she replied: ‘‘Are you from Harooraa’ (meaning are you from the Khawaarij? because they are used to be extravagant) and then she said: “We were ordered to make up for the fasting but we were ordered not to make up for the prayer.”
There is no doubt that there is much wisdom in determining the types of Zakah and their amounts. To know some of this wisdom, you may refer to what Ibn Al-Qayyim wrote about this wisdom in his book “Zaad Al-Ma’aad.” He entitled a Chapter: A Chapter about the guidance of the Prophet on charity and Zakah…etc. In this chapter, he stated much wisdom for determining the types of wealth on which Zakah must be paid and determining its due time and the wisdom behind determining its amount according to its specification in the Sharee’ah.
As regards the owned land, if it is not purchased in order to trade in it, then there is no Zakah on it as the Prophet said: “A man is not obliged to pay Zakah on his slave and his horse.” [Al-Bukhari and Muslim]. For more benefit, please refer to Fataawa 86227 and 88986.
Allaah Knows best.