Those who don’t give Zakaat – Their bodies will be branded
Allah Most High 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: 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 the Day of Judgment 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 a day, 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 paradise 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 and 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 the Day of Judgment, 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 a day 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 paradise 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), on the Day of Judgment, 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 paradise or hell. (Sahih Muslim, Hadith No. 2337)