It is given in the Holy Quran:
And those who are niggardly in giving away (from the wealth) which Allah has bestowed upon them out of His bounty must never consider this miserliness of any benefit for themselves; it is rather injurious to them. Soon on the Day of Resurrection this wealth, which they are niggardly about, will be put around (their necks) like a neck-fetter. To Allah belongs the heritage of the heavens and the earth (i.e. He will remain the Owner of the universe after your death in the same way as He owns it today). And Allah is Well Aware of all your deeds. Surah Al Imran (3:180)
(Sahih Bukhari, Hadith No. 1403)
With the aforementioned verse of the Holy Quran, it is clear that the wealth of the affluent is a grant of Allah Ta’ala. Allah Ta’ala has given them that only out of His benevolence. If wealth had been gained by personal effort and physical and mental capability, then no hard working, healthy person would have been needy. No intelligent person would have been poor although it is not so. Thus, the affluent folk should thank Allah Ta’ala and should remember the poor and needy folk.
Those who don’t give Zakaat – Their bodies will be branded
Allah Ta’ala says:
O Believers! Indeed the majority of the priests and monks (of the People of the Book) devour the wealth of the people through unfair (means) and hinder from the path of Allah (i.e. fill their safes with people’s money and hinder it from being spent for the publicity and promotion of the True Din [Religion]). And those who hoard silver and gold and do not spend it in the cause of Allah, warn them of a grievous torment.
The Day when this (gold, silver and wealth) will be heated in the Fire of Hell, their foreheads, sides and backs will be branded with this (heated material, and it will be said to them:) ‘This is the same (wealth) that you treasured for (the benefit of) your souls. So taste (this wealth) which you had been amassing.’ Surah Taubah (9:34-35)
There are severe warnings for those who don’t give Zakaat in Sahih Muslim, which act as the exegesis of the aforementioned verse of the Holy Quran:
Translation of Hadith: Hadhrat Abu Hurairah (May Allah be well pleased with him) says that the Holy Prophet (Sallallahu alaihi wa sallam) said: The person who has gold and silver and does not fulfill its rights (i.e. give Zakaat), on Qiyamah mountains of fire will be made for that person and he (or she) will be heated with it and his (or her) flanks, forehead and back will be branded with it. Whenever those mountains cool down, they will be reheated and this person will be punished. For days, which will be like 50,000 years, this will go on continuously. At last, when the reckoning of all people will be over, they will be shown the way to Jannah or hell.
The Holy Prophet (Sallallahu alaihi wa sallam) was asked: O Prophet of Allah (Sallallahu alaihi wa sallam)! What will happen to those who own camels? The Holy Prophet (Sallallahu alaihi wa sallam) said: The camel-owner who does not fulfill the rights of the camels. Among their rights is that the day camels are watered, they should be milked and the milk should be given to poor people. For the person who doesn’t give their Zakaat, on Qiyamah they will be laid face down in a plain. Then those camels will come. They will be fat and plump. Not even a small calf will be missing that day. They will trample that person with their hoofs and bite them. When one train of camels goes away, another will come. For days which will be like 50,000 years, this will go on. Eventually when the reckoning of all people will be over, then they will sent on to Jannah or hell.
The Holy Prophet (Sallallahu alaihi wa sallam) was asked: O Prophet of Allah (Sallallahu alaihi wa sallam)! What about those with cattle and sheep? The Holy Prophet (Sallallahu alaihi wa sallam) said: Those with cattle and sheep who don’t fulfill their rights (i.e. does not give Zakaat on them), in Qiyamah, that person will be made to lie in a flat plain. All the cattle, there will be none missing among them, and goats will strike that person with their horns and trample them with their hooves. On that day, they will be none with backward-growing horns, neither any without horns nor any with broken horns. After one flock passes away, another will come and for a day worth 50,000 years, this will go on happening. At last, when the reckoning of people has been done, he (or she) will be sent to Jannah or hell. (Sahih Muslim, Hadith No. 2337)
Those who don’t give Zakaat will be in trouble in Qiyamah
There is a Hadith in Sahih Muslim:
Translation: Hadhrat Abu Dhar (May Allah be well pleased with him) says that I went to the Holy Prophet (Sallallahu alaihi wa sallam). He was sitting in the shadow of the Ka’aba. One seeing me, He said: By the Lord of the Ka’aba! They will be ruined. I sat down, but then stood up out of restlessness and said: O Prophet of Allah (Sallallahu alaihi wa sallam)! I would offer my mother and father in lieu of you! Who are they? The Holy Prophet (Sallallahu alaihi wa sallam) said: They are the mighty rich except those who spend in front, this side, that side and behind them and rich people like this are very rare. The person who has camels, cattle or goats and does not give Zakaat on them, in Qiyamah they will all come fatter than they had ever been and will strike that person with their horns and trample him (or her) with their horns. When the last animal will have finished trampling, the first will return to trample and until the reckoning of the people is over, this will go on happening. (Sahih Muslim, Hadith No. 2347)
Punishment with hot stones of hell
Translation of Hadith: It has been narrated on the authority of Hadhrat Ahnaf Bin Qais (May Allah be well pleased with him), he says: I came to Madina. I sat in a group in which there were chiefs of Quraish. Suddenly a person who was wearing coarse clothes came to them. He was dignified and his face, awe-inspiring. He stood near them and said: Give tidings of that stone to those who hoard wealth, which will be heated in the fire of hell and that stone will be placed on their nipples, which will then burst from the bones of the shoulder and it will be placed on the shoulder and it will burst out through the nipple and that stone will continue going through and through like that.
The narrator says: Those people lowered their heads and I didn’t see any one of them answering to Him. (Sahih Muslim, Hadith No. 2353)