Muwatta Imam Malik Book of Zakat, Hadith 12

Yahya related to me from Malik that he had heard that Umar ibn al-Khattab said, "Trade with the property of orphans and then it will not be eaten away by zakat."

حَدَّثَنِي يَحْيَى، عَنْ مَالِكٍ، أَنَّهُ بَلَغَهُ أَنَّ عُمَرَ بْنَ الْخَطَّابِ، قَالَ اتَّجِرُوا فِي أَمْوَالِ الْيَتَامَى لاَ تَأْكُلُهَا الزَّكَاةُ .