(11) باب مَا لِلْوَصِيِّ مِنْ مَالِ الْيَتِيمِ إِذَا قَامَ عَلَيْهِ
It was narrated that Ibn 'Abbas said -concerning the Verse:
"Verily, those who unjustly eat up the property of orphans" -A man would have an orphan in his care, and he would keep his food, drink and vessels separate. This caused hardship to the Muslims, so Allah, the Mighty and Sublime, revealed: "And they ask you concerning orphans. Say: The best thing is to work honestly in their property, and if you mix your affairs with theirs, then they are your brothers" (in religion), so it is permissible for you to mix with them.
Reference: Sunan an-Nasa'i 3670
In-book reference: Book 30, Hadith 60
English translation: Vol. 4, Book 30, Hadith 3700