Nafi' reports: Abdullah bin Umar (may Allah be pleased with them) had the wealth of an orphan in his possession. He would sometimes take a loan from it, and at times he would become its guarantor. And when he became the guardian of the orphan's wealth, he would also pay its zakat.
Hadith Referenceسنن الدارقطني / كتاب زكاة / 1976
Hadith Takhrij«أخرجه البيهقي فى((سننه الكبير)) برقم: 7441، 7716، 11098، 11099، 11722، 12800، والدارقطني فى ((سننه)) برقم: 1976، 1978، وعبد الرزاق فى ((مصنفه)) برقم: 6992»