Responsa על נדרים 129:4

Response: This man married this woman knowing that she could no longer have children, but was very wealth. He married her for money and swore that he would not marry a second wife. He did not make the oath conditional. Rather, he swore straightforwardly. What wise man would attend to him, releasing him from his oath, when he swore to allay the woman’s thoughts, so she would marry him? No wise man would release him. As it is stated (Nedarim 65b): “You vowed in Midian? Go release your vow in Midian.”