The enemies of Ali (a.s) also confessed to his generosity. It is mentioned in Matalibus So’ool that when Mahqan Ibn Abi Mahtan told Muawiyah that he had come to him from the greatest miser. Muawiyah said, “Woe be to you. Do you call Ali a miser? If he is given a house of gold and a house of straw, before the house of straw, the house of gold would be finished.”
Shoba has written that Ali (a.s) was so generous and he liked giving charity so much that he never uttered ‘No’ to anyone who asked him for something. He used to irrigate the farms of a Jew, himself, till he got boils on his palms and whatever he earned therefrom, he gave it all in charity and in order to control his hunger he tied a stone on his stomach.
Reference :Akhlaq al-A’imma, Morals & Manners of the Holy Imams