Is it permissible for a wife to sell her gold without her husband's knowledge to pay her university tuition fees, which the husband promised to pay then reneged on, in light of her father's inability to pay and the university's threat of legal action?

The husband is not obligated to pay for his wife's tuition fees because this is not part of the obligatory maintenance. However, it is recommended for him to pay them, either to fulfill his promise or as an act of kindness towards his wife. It is permissible for the wife to sell her personal gold to cover the fees, even without her husband's permission, though it is recommended to inform him. However, if the gold belongs to the husband, she is not allowed to sell it without his permission.