It was narrated from Muhammad bin Ka`b al-Qurazi that ‘Ali (رضي الله عنه) said:
I remember when I was with the Messenger of Allah (ﷺ) and I tied a rock to my stomach because of hunger, and now my zakah is forty thousand.
It was narrated from `Ali (رضي الله عنه)... and he mentioned the same hadeeth, and said in it. The zakah of my wealth is forty thousand dinars.