The Case of One Who Vows to Fast a Certain Day or for Thanksgiving

9. Muhammad ibn ‘Isma‘il has narrated from al-Fadl ibn Shadhan from Ibn Abi ‘Umayr from Ibrahim ibn ‘Abd al-Hamid who has said the following: “I once asked abu al-Hassan, al-Rida’ عليه السلام, about a man who places upon himself for Allah, most Majestic, most Glorious, fasting of a definite day. He (the Imam) said, ‘He is required to fast definitely, regardless of being on a journey or at home.’”