Sunnah.com reference : Book 4, Hadith 11English translation : Book 4, Hadith 632Arabic reference : Book 4, Hadith 608
Amro bin Shu’aib narrated on the authority of his father who reported on the authority of his grandfather, on the authority of Abdullah bin 'Amro(RAA) that the Messenger of Allah (ﷺ) said:
“One who becomes the guardian of an orphan, who owns property, must trade on his behalf and not leave it (saved and unused) until it is all eaten up by Zakah (which is paid yearly).” Related by At-Tirmidhi and Ad-Daraqutni with a weak chain of narrators.
وَعَنْ عَمْرِو بْنِ شُعَيْبٍ, عَنْ أَبِيهِ, عَنْ جَدِّهِ; عَبْدِ اَللَّهِ بْنِ عَمْرِوٍ; أَنَّ رَسُولَ اَللَّهِ ‏- صلى الله عليه وسلم ‏-قَالَ: { مِنْ وَلِيَ يَتِيمًا لَهُ مَالٌ, فَلْيَتَّجِرْ لَهُ, وَلَا يَتْرُكْهُ حَتَّى تَأْكُلَهُ اَلصَّدَقَةُ }  رَوَاهُ اَلتِّرْمِذِيُّ, وَاَلدَّارَقُطْنِيُّ, وَإِسْنَادُهُ ضَعِيف ٌ  1‏ .‏‏1 ‏- ضعيف.‏ رواه الترمذي ( 641 )‏، وضعفه، والدارقطني ( 2 / 109 ‏- 110 )‏.‏