Is it permissible to take money from one's father to buy clothes for him without his knowledge, with the intention of returning the money later after graduation and employment?

The general rule is that a Muslim's property is inviolable unless given willingly. An exception to this is the obligatory maintenance for a wife and children; they are permitted to take what is customary without the husband's knowledge. However, it is not permissible to take money from a father without his knowledge. Instead, persuade him to buy clothes for himself in various ways. If he does not respond, then it is incumbent upon his children to remind him of the necessity of buying clothes for himself.