It is narrated from Abdullah bin al-Samit (may Allah have mercy on him) that Sayyiduna Abu Dharr (may Allah be pleased with him) took his stipend (allowance) and went with a servant to the market to buy what he needed. Then, with whatever was left, he bought copper coins (fulus) and gave them away in charity. Then he said: "I heard the Messenger of Allah (peace and blessings be upon him) saying: 'Whoever ties up gold or silver and stores it away, and does not spend it in the way of Allah, it will become a burning coal on the Day of Resurrection with which he will be branded.'"
Hadith Referenceالمعجم الأوسط / باب الميم / 5470
Hadith Takhrij«أخرجه الطبراني فى «الكبير» برقم: 1641»