Holy Quran conveys a severe warning for those who do not pay Zakat, as it is stated in part 10, Surah At-Taubah, verse 34:

وَ الَّذِیْنَ یَكْنِزُوْنَ الذَّهَبَ وَ الْفِضَّةَ وَ لَا یُنْفِقُوْنَهَا فِیْ سَبِیْلِ اللّٰهِۙ-فَبَشِّرْهُمْ بِعَذَابٍ اَلِیْمٍۙ(۳۴)

And those who pile up gold and silver and do not spend in the Way of Allah; give them glad tidings of a painful punishment.^[1]

Listen to two blessed sayings of the Holy Prophet صَلَّى الـلّٰـهُ عَلَيْهِ وَاٰلِهٖ وَسَلَّم containing warnings for those who do not pay Zakat:

1.   Three people will enter Hellfire before anyone else. One of these is the wealthy person who does not fulfil the right (Zakat) of Allah Almighty.

2.   Whoever owns gold or silver and does not fulfil its right (i.e., Zakat), slabs of fire will be laid out for him on the Day of Judgement, which will be heated in the fire of Hell. Their sides, forehead and back will be branded with them. Whenever they begin to cool, they will return to their original state. (This will continue to happen) on that Day whose length is 50,000 years; until judgement is made regarding people. He will then see whether his path leads to Paradise or Hell. ^[2]

Dear Islamic brothers! Without doubt, Allah is Most-Wise, and His every action has infinite wisdom behind it. Whatever rulings He has ordered upon His servants are all filled with wisdom and meaning. It is the shortcoming of our limited minds which leads us to not understanding this.