if we were to prevent his disposition with permission, we would have no way of knowing his maturity and testing him. The second view is that it is not valid, because the interdiction upon him is due to his profligacy and poor judgment; so if he grants him permission, he has permitted that which has no benefit, and it is not valid, just as if he permitted the sale of what is worth ten for five. Al-Shafi'i has two views like these. And Allah knows best.