It is narrated from Hasan al-Urani (may Allah have mercy on him) that a man came to the Prophet (peace and blessings be upon him) and said: There is an orphan under my care; may I beat him? He (peace and blessings be upon him) said: "(Only) when you would beat your own child for the same." He said: May I eat (from his wealth)? He (peace and blessings be upon him) said: "In a fair manner, without accumulating wealth (for yourself), and without protecting your own wealth by means of his wealth."
This is mursal; it has also been narrated through another route as connected (mawsul), but that is weak, and it has already been mentioned in the Book of Sales.
Hadith Referenceالسنن الكبرى للبيهقي / كتاب الوصايا / 12672
Abu Raja' (may Allah have mercy on him) said: Sayyiduna Umar bin al-Khattab (may Allah be pleased with him) said: May Allah Almighty have mercy on a man who strikes an orphan in order to teach him manners.
Hadith Referenceالسنن الكبرى للبيهقي / كتاب الوصايا / 12673
Shumaysah said: I asked Sayyidah Aishah (may Allah be pleased with her) about disciplining an orphan, and she said: I strike one of them until he becomes cheerful.
Hadith Referenceالسنن الكبرى للبيهقي / كتاب الوصايا / 12674