Rasul Allah (sal Allahu alaihi wa sallam) said: “What disease is worse than stinginess?” [Sahih Bukhari]
Disease ruins the health of the body. When a person has the flu his/her whole body feels weak. It is only when he/she recovers that strength comes back to their limbs. If the person had to live with flu the rest of their life it would be a compromised existence. As flu is a disease of the body, stinginess is a disease of the soul. It ruins the health of the soul and eeman becomes weak. As long as the person does not recover from stinginess the condition of his/her eeman remains poor and the person is not able to do much good.
Allah (subhana wa ta’ala) says: “Here you are, called upon to spend in the Path of Allah, and some of you are being stingy, while whoever is stingy is only ungenerous towards himself. It is Allah who is rich and you who are the poor.” [Quran 47:38]
Allah (subhana wa ta’ala) is reminding us in this ayat that He has no need for our donations whatsoever. Whatever we have was given to us by Him who owns all the treasures in the universe and much, much more. When we are called to spend in the Path of Allah it is just to see who is stingy in giving back to Allah (subhana wa ta’ala) and who believes and trusts in Allah (subhana wa ta’ala) and is anxious that a home is made for him/her in Paradise.
The person who is niggardly in spending in Allah’s Path is actually being ungenerous only towards himself. This is because whatever we spend in Allah’s Path is what we are spending on our own home in Jannah. In fact, Allah (subhana wa ta’ala) multiplies what we spend and gives it back to us both in this world as well as putting it towards our homes in Jannah. Thus, the miser is only miserly towards himself/herself.
Uthman (radi Allahu anhu) was a man who would spend his wealth freely in the Path of Allah seeking the pleasure of his Lord. Abu Hurairah (radi Allahu anhu) narrated: “Uthman bought Jannah from Allah’s Messenger twice: 1) Once in a business transaction when he bought the well of Rumah (from the disbelievers), and which he made a public property for all Muslims, and 2) he bought it a second time when he fully financed and equipped the Army of Hardship (Jaish al-Usra).” The Army of Hardship was the name given to the Muslim army when it marched out to confront the Romans in Ghazwa Tabuk. This was a very difficult journey for the Muslims to undertake, which is why their army was called the Army of Hardship. Uthman (radi Allahu anhu) gave so much to finance this Ghazwa that the Prophet (sal Allahu alaihi wa sallam) said: “Uthman does no longer need a deed of righteousness (i.e. to please Allah) after this.” [The Beauty of the Righteous and Ranks of the Elite by Imam Abu Naim al-Asfahani]
Stinginess when it comes to spending in the Way of Allah is classified as an enormity (kaba’ir) by Imam Dhahabi in his Kitab al-Kaba’ir (Book of Enormities).