the Prophet addressed the people and said: "As for one who is the guardian of an orphan who has wealth, then let him do business with it and not leave it until it becomes consumed by charity."  

أَنَّ النَّبِيَّ ﷺ خَطَبَ النَّاسَ فَقَالَ أَلاَ مَنْ وَلِيَ يَتِيمًا لَهُ مَالٌ فَلْيَتَّجِرْ فِيهِ وَلاَ يَتْرُكْهُ حَتَّى تَأْكُلَهُ الصَّدَقَةُ