Is the son obligated to pay his university tuition expenses to his parents, which have become a debt on him, according to his mother?

Expenses for education are not included in the obligatory maintenance (nafaqa) a father owes his child. What a person spends as maintenance, not being legally obligated to do so, with the intention of volunteering it (as a gift), he does not have the right to reclaim, based on the Prophet's (peace be upon him) saying: "The one who takes back his gift is like a dog that returns to its vomit; we do not have such a bad example." However, if he spent with the intention of reclaiming it, he has the right to reclaim it if he can prove that with evidence. The intention of volunteering is the default, as is customary. The son should be good to his parents and dutiful towards them, and if they are in need of maintenance and he is well-off, it is obligatory for him to provide for them.