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.
Related:
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 Night Journey/17:35
When you measure, measure precisely and weigh with accurate scales. Surely that is better and the result is better
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.