Is a vow not to marry until one's mother memorizes three parts of the Qur’an, which has caused distress to the mother, considered an act of disobedience (ʿuqūq), and is it permissible to marry before she completes her memorization?

It is not permissible to oblige the mother with what is not religiously obligatory upon her, especially if it causes her hardship. If the mother cannot memorize the Qur'an except with extreme difficulty, she should not be obliged to do so. A vow intended to urge someone to do a specific act has the same ruling as an oath. Therefore, one must apologize to the mother and appease her, and offer expiation for breaking an oath. By doing so, the vow is dissolved, and the mother is not required to memorize what she cannot bear. As Ibn Qudamah said: "A vow that is in the nature of an oath, intended to urge or prevent something, without intending it as a vow or an act of closeness [to Allah], its ruling is the same as that of an oath."