Al-Hakam bin Abi al-As said that Sayyiduna Umar (may Allah be pleased with him) said: "Do you have any trade? I have an orphan's wealth that is about to be used up by the payment of zakah." I said: Yes. He said that he gave me ten thousand, and I was away with that wealth for some time. Then I returned to him, and he asked me about it: "What became of the wealth?" I said: It has become one hundred thousand. He said: "Return our wealth to us; we have no need of the trade."
Hadith Referenceالسنن الكبرى للبيهقي / كتاب البيوع / 10985