The Cattle - 6:152
Do not approach the property of orphans until they reach the age of maturity. Measure and weigh accurately. We do not burden a person with what he is not able. When you speak, be truthful even against your relatives. Keep your promise to Allah. These are His admonitions to you that you may take a lesson.
Do not approach the property of orphans until they reach the age of puberty, unless it is for their benefit:
The Night Journey/17:34
Do not touch the property of orphans until they reach the age of maturity, except for their benefit. And fulfill your promises. For you will be held accountable for what you have promised.
The Women/4:6
Test the orphans when they reach the age of marriage. If you see maturity in them, give them their property. Do not eat their wealth in extravagance and haste, lest they grow up. Let the rich give up (the wages of his efforts to protect the property). Let the poor spend an appropriate amount. Return their property to them in the presence of witnesses. Allah is sufficient as the Reckoner.