Abū Hurairah relates Allah’s Messenger ﷺ as saying: “If an owner of gold or silver does not pay what is due to him, when the Day of Resurrection would come, plates of fire would be beaten out for him; these would then be heated in the fire of Hell and his sides, his forehead and his back would be cauterised with them. Whenever these cool down, (the process is) repeated during a day, the duration of which would be fifty thousand years, until judgement is pronounced among servants, and he sees whether his path is to take him to Paradise or to Hell.…”
(Muslim)
There is grave punishment in the Day of Judgement for the wealthy who refuse or do not care to pay Zakat.
If the owner of gold or silver of the specific measure or equivalent cash does not pay Zakat, Allah’s Messenger warns him against unending process of grave punishment. The specified punishment for a non-payer of Zakat is cauterising his sides, forehead and back with the plates of fire beaten out and then heated in the fire of Hell. When these plates cool down, the process would be repeated until the judgement is pronounced. The punishment of burning the body parts continues for the whole Day of Judgement, which would be as long as fifty thousand earthly years.
The Messenger ﷺ added that the camel, sheep or cattle will trample its owner if he fails to pay Zakat, with their hoofs and bite him with their mouths, until the judgement is pronounced.