Translation:

6. Make trial of orphans until they reach the age of marriage; if then ye find sound judgment in them release their property to them; but consume it not wastefully nor in haste against their growing up. If the guardian is well-off let him claim no remuneration but if he is poor let him have for himself what is just and reasonable. When ye release their property to them take witnesses in their presence: but all-sufficient is Allah in taking account.

Notes (Tafseer)

512. The age of marriage is the age when they reach their majority.

513. It is good to take human witnesses when you faithfully discharge your trust; but remember that, however fully you satisfy your fellow-men when you give your account to them, there is a stricter account due from you to Allah. If you are righteous in Allah's eyes, you must follow these stricter standards.