The Factors that Constitute Marriageable Age
And test orphans (in their intelligence and abilities) until they reach marriageable age. If you then observe sound judgement from them, release their property to them, and do not consume it without due right, exceeding the limit thereby, and (nor consume it) hastily lest they grow up (whereupon you have to return it to them). And whoever (among the guardians) is rich, he should refrain (from taking a fee for his guardianship), but if he is poor, then let him take according to what is just and reasonable. So when you release their property to them, bring witnesses over them and sufficient is Allāh in taking account. Qur'an 4:6

And do not approach the orphan's property except (to increase it through trade) in a way that is best until he reaches (mental and physical) maturity. And give full measure and weight in justice. We do not task any soul except with what lies in its capacity (to bear). And when you testify, be just, even if (it concerns) a near relative. And fulfill the covenant of Allāh. This is what He has instructed you so that you may remember. Qur'an 6:52
And when the children among you reach puberty, let them ask permission [at all times] as those before them have done. Thus does Allah make clear to you His verses; and Allah is Knowing and Wise.
Qur'an 24:59.
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